Warlock Patrons of Azeroth

 The WoW D&D book is going to give a lot of guidance for player to re-create WoW classes and specializations within D&D rules. In some cases, this will be trivial: a Guardian or Feral Druid can just go Circle of the Moon (though I'd freaking love it if they create a scaling template for Bear and Cat forms we could use at any level). But in some cases, namely the Death Knight and Demon Hunter, they'll be doing some unprecedented re-works of existing classes and creating subclasses that are sort of more than subclasses and really extensive re-works of the base classes they're being grafted onto (we've only seen level 1 and 2 features for Ebon Blade Paladins, which replace Lay on Hands and Paladin's Smite - though Rune Strike, which replaced Divine Smite, is basically the same spell except it does Necrotic damage and only gets a bonus die against Celestials).

But while it could be fun to play with restrictions to require players to build characters to fit with WoW's existing classes and specs, I think think it would be more fun to take adventures in Azeroth to places you can't replicate in the MMO.

Let's consider the Warlock.

In D&D, of course, a Warlock is a character who has forged a pact with a powerful magical entity (though 5.5 broadens this a bit to allow you to draw from multiple sources, as long as they're sort of in the same category.

By contrast, Warlocks in World of Warcraft are scholars just like Mages (the Wizard equivalent,) but while Mages study in very socially-acceptable learning institutions (though for a long time, their practices were forbidden among the Night Elves,) Warlocks are scholars of forbidden knowledge, specifically the knowledge of Fel magic, which is the inherently destructive power that suffuses demons.

Warlocks in WoW have three different specializations, like most classes, but all three are still Fel/demonic magic. Affliction is the one that might be easiest to reflavor as instead some kind of necromancy, but the other two, Destruction and Demonology, are both firmly in that Fel/Demon category (Destruction focuses more on blasting foes with demonic fire and raw chaos while Demonologists summon tons of demons to attack their foes).

D&D's Warlocks, thus, have a broader array of options in where they get their magic, and so I figured what I'd do is go through each Warlock subclass and talk about what kinds of patrons you might choose.

    Archfey:

While WoW doesn't have a Fey creature type, they do have some entities that would probably fit with the Fae, most notably the explicitly named Night Fae, who are the caretakers of the realm of Ardenweald, one of the afterlives in the Shadowlands. Here, natural creatures and people dedicated to nature go to take part in the cycle of life, eventually being reborn in a cycle of reincarnation. The Winter Queen is the leader of the Night Fae. But more broadly, the Wild Gods might fit this category - Wild Gods cover a lot of animal spirits worshipped or revered by various cultures across Azeroth. The Night Elves have their Ancients (not to be confused with the giant walking trees also called Ancients, who are... also nature spirits of course, but in a less divine way,) the Trolls have their Loa (which also include some beings that aren't quite as animalistic or even associated with nature) and the Pandaren have their August Celestials. Even the Orcs have animal gods like Lo'gosh (who might actually be the same as the Night Elves' Goldrinn...?) While not necessarily as fickle and tricksy as Fey tend to be, these are probably your best equivalents.

    Celestial:

It's really up in the air which of WoW's creatures would count as Celestials, but the ones that I don't think you could argue against are the Naaru. These are crystalline beings of pure holy light that are particularly important to Draenei culture. While it's supposed to be very rare, in game we often see Naaru go through a horrible cyclical transformation, turning to the Void as Dark Naaru (who are probably more on the Aberration/Great Old One side of things). Other options potentially include, actually, the Titans or their Titanforged creations. While the Titanforged act very much like constructs, beings like Tyr, Odyn, Thorim, Freya, Mimiron, or Ra-Den (the latter of which is dead by the end of Battle for Azeroth, but then, Tyr was dead for a very long time before we brought him back during Dragonflight) I think they'd fit pretty well in this category as well.

    Fiend:

I mean, there's plenty of demons in WoW. Warlocks in World of Warcraft tend to invert the patron relationship, with demonic minions bound to serve Warlocks through contracts that make any Warlock worth their salt the more powerful person in the relationship, but bargaining with power from a powerful demon certainly feels plausible on Azeroth. I think you could play a Fiend Warlock easily enough as a standard WoW warlock (just remember that Fel fire is typically green!) Another possibility is actually Illidan Stormrage. While sort of a half-demon (though he sure looks more demonic than even the Demon Hunters who he's trained) Illidan is WoW's ultimate edgelord antihero, a firm and hard Chaotic Neutral. (Also, Critical Role fans, if you didn't know already for some reason, will be excited to know that he's voiced by Liam O'Brien!) But also a somewhat more benign source of Fel power.

    Great Old One:

Two really great categories here: The most obvious is the Old Gods. While all four of Azeroth's Old Gods are (in theory) dead in the current state of the game, we did have to kill three of them as the final bosses of their respective raids (well, there was an optional extra-hard boss in Ulduar after Yogg-Saron). But these ancient flesh-mountain monstrosities certainly fit the bill. Alternatively, you could go for something less fleshy and more cosmic with the Void Lords. The only one of these we've ever actually seen or had named is Dimensius the All-Devouring (who was the final boss of the last expansion) but I think you could lean into the mystery of what your patron is if you went with an unnamed Void Lord. (The game's current antagonist, Xal'atath, and likely the final boss of the current expansion, is a former mortal turned void-entity that was probably not a true Void Lord, but might fit this, though she'd be an absolute perfect Hexblade patron).

    Undying:

This subclass... is weird because it could just be an undead patron, but it's also explicitly not just undead beings. If you for some reason really wanted to play this not-very-good and conceptually thin subclass, though, there are tons of extremely old beings on Azeroth. Maybe you go with Nozdormu, the Bronze Aspect, leader of the dragons who manage and safeguard the timeline (or his alternate-timeline-self nemesis, Murozond).

    Hexblade:

There are a few sentient weapons, most notable of which was Xal'atath, Blade of the Black Empire, which was the artifact weapon granted to Shadow Priests during the Legion expansion, but whose resident conscious being transferred into the body of a dead elf (that we provided for her) and has now been leading a deadly assault on Azeroth with her void-creature army called the Devouring Host. Two other weapons for Legion had personalities, with Aluneth, a staff that contained a powerful arcane consciousness, and the Skull of the Man'ari, the remains of an Eredar summoner who got into demonology before it was cool on Argus and ironically was arrested by future demon lord Archimonde for dabbling in such magic. Other weapons like Ashbringer, Doomhammer, or Frostmourne might fit here, though it's dubious whether they're actually sentient (technically I guess Frostmourne might be a conduit for the Jailer).

    Genie:

WoW does have genies, but they're a pretty rare category specifically of air elementals. If you wanted to take the idea of a powerful elemental, you could possibly instead go with the Elemental Lords, of which there are conveniently one for each element. The OGs are Ragnaros the Firelord, Al-Akir the Windlord, Neptulon the Tide-Hunter, and Therazane the Stonemother. However, there's been some turnover over the course of WoW. Ragnaros is dead, and was replaced by Smolderon, though we also had to take him down as well (though this was outside of the Firelands, so I actually think he's probably still alive and still the Lord of Fire). We killed Al-Akir as well, though his son Thunderaan I believe remains the Windlord. Basically, depending on when in WoW's timeline you want to set your campaign, you might need to pick alternatives. Note that the elemental lord of Draenor, the Orcish homeland (and sort of adopted Draenei homeland, though they were only there for about a thousand years, which isn't much for a people who seem to naturally live to be tens of thousands of years old) you could pick them.

    Fathomless:

Ok, there are probably some other options here, but I think the best one is Queen Azshara. Once the radiant and beautiful queen of the Night Elves in ancient times, when her capital sank beneath the waves, she struck a deal with the Old God N'zoth to save her people by transforming them into the serpentine Naga. Azshara is one of Azeroth's most dangerous villains, but she's a pragmatic and patient one (while her royal palace in her capital, now called Nazjatar, was a raid with her as the final boss, she survived this attack and we actually wound up rescuing her from N'zoth, a decision that will probably bite us in the ass somewhere down the line).

    Undead:

Boy howdy. So, the obvious options here would be members of the Scourge. The most powerful of which is certainly the Lich King. But if you're playing in a post-Wrath timeframe, the Lich King could be Bolvar Fordragon, a heroic paladin who sacrificed his freedom to try to hold the Scourge on a tight leash, and while Bolvar certainly did some questionable things as Lich King, he was certainly more benevolent than Arthas had been. WoW does have its fair share of Liches and Death Knights. I actually think making the entire Knights of the Ebon Blade a patron could be fun, or perhaps specifically having the Four Horsemen, the Ebon Blade's most elite knights (aside from the Deathlord, the player character, of course) as your patron would allow a DM to play the varying personalities between them (this latter option doesn't totally work if you're doing the Scarlet Monastery dungeon, as I'm confident its final boss will be High Inquisitor Whitemane, who is later raised as a death knight and becomes one of the Four Horsemen, ironically "redeeming" herself by becoming an undead killing machine. Better than a religious fundamentalist!)

    Vestige:

This new subclass from Arcana Unleashed ironically might actually make you play a little more like a WoW Warlock, who generally have a minion fighting alongside them in battle. (I play a Demonology one, who would always have a minion out, but I can't remember if the other two specs even have the option to not play with one). But mechanics aside, I do think there are some options here, even if they're a bit non-obvious. We have a few dead god-like beings, such as the nascent Titan Argus, or the lost (and very much beloved - the fans got up in arms) bear ancient Ursoc. Rezan, the Zandalari Troll Loa of Kings (he's a T-rex!) died to the treachery of the Prophet Zul. It also turns out that the Titans were, actually, for most of WoW's history, already in a state of more or less death - Sargeras slew them right around the time that he founded the Burning Legion, and it wasn't until we liberated their tortured souls at the end of the Legion expansion that they were able to return to their full power.

I think that's all of them? I'm actually quite pleased that there seems to be at least one pretty good option for every subclass, and there are probably more if you go digging.

Ironically, though, I think you could argue that these subclasses almost see representation in other classes in WoW. Shadow Priests, for example, have some abilities based around the Old Gods. And actually, the lore of the Shaman class is that they act essentially a mediators and negotiators between elemental spirits, which I actually think is pretty Warlock-coded (though it seems they'll be represented more by Barbarians - which is surprising on a mechanical level but sort of makes sense as two classes really deeply rooted in ancient/primal powers).

Vestige Lock vs. Wyvern

 The Vestige Patron for Warlocks is one of the most buzz-generating subclasses to come out of Arcana Unleashed. Your patron is a dying god, who manifests as a companion pet that fights alongside you in battle. It's a really interesting inversion of the usual patron/warlock dynamic, and while I think you could certainly flavor it more as your patron manifesting an avatar to serve you, the biggest deal, I think, is that it's a Warlock pet subclass.

As someone whose first class-based RPG was World of Warcraft, Warlocks and Hunters (er, Rangers) have always felt natural as pet classes. And indeed, we'll be able to come with many flavors of pet, as the vestige can be undead, celestial, or fiend, with slightly different abilities depending on your choice.

So, how do we want to build this thing? While Pact of the Blade can be a higher damage option, I think here we're going to go the classic Blastlock route. Admittedly, if you play with Flanking (which appears nowhere in the 5.5 official rules, by the way) you might be inclined more toward Pact of the Blade, but I think my general assumption is that most Warlocks prefer to stay at range.

Unlike other pet subclasses, our companion can actually make ranged attacks as well, so if we want to keep both ourselves and our friend at a safe distance, we'll just hang back and lob attacks from afar.

Because we're building to level 10, we'll be skipping out on the 14th level feature (which is actually pretty great - eventually giving you essentially an extra 9th level slot to cast a Summon spell).

Ok, let's get into it:

As usual, we'll be looking to use a good concentration spell, and one that won't take up our bonus action, as we'll need that for the companion. I'll note as well that we might consider picking up Battle Familiar, which is available to Warlocks and doesn't require concentration. Like the Summon spells we get, it's fire-and-forget. Pact of the Chain is all well and good, but it's usually not worth sacrificing one of your attacks for the familiar's attack (and if we're using Eldritch Blast, we aren't taking the attack action anyway).

At 5th level, our Battle Familiar will be making two attacks that deal 12.5 force damage per hit. We might go with the Flyer to let them dodge in and out of melee range - they only have a 30 foot fly speed, so the safest bet is to fly 15 feet above a target and then dive-bomb them.

But that leaves a concentration slot open. I actually really like the utility that Summon Undead gives, but the math on whether, say, the Putrid one actually poisons and then paralyzes the target can get pretty messy. We might instead choose the Skeletal version to just do some pure damage, and again, at range where we and our vestige will be hanging out.

Essentially, once we have all of this up and running, we can have four creatures (us, our familiar, our skeleton, and our vestige) all bombarding the target with ranged attacks. There are two rounds of set up required, but both Battle Familiar and Summon Undead last an hour, so we could get this running if we know we're going into a fight.

Mind you, we choose one of the Domain Spell lists from the PHB, which function as our patron spells for this subclass. While Crusader's Mantle from the War Domain could be great, our pets aren't using weapons (technically the Battle Familiar would be considered to be making natural weapon attacks, at least in 5.0, but it's a little less clear in 5.5). Thus, I think we stick with these. That's going to take both of our spell slots at level 10, so this is an all-out option, but again, at an hour duration for both spells, we might be able to keep it up through multiple fights.

For invocations, we're obviously grabbing Agonizing Blast. I think that's the only one that's going to directly improve our damage output, but grabbing things like Repelling Blast, maybe even Gift of the Protectors to keep our minions alive, could be good.

Note that if we are casting both Battle Familiar and Summon Undead, we're going to be unable to use Vestige Recovery mid-combat, but again, we're staying at range, so hopefully our buddy isn't going to be getting hit.

    Now, feats:

As usual, I'd generally say grab War Caster and then, as a Charisma-based character, we can pick up Inspiring Leader. The tough thing here is that we probably won't be able to buff our Undead and Battle Familiar with this because it takes a short rest, which will eat up the hour that they last.

Anyway, if we're willing to delay capping Charisma, we should have a Charisma of 19 at level 10, for a +4.

So, let's do the damage calculation!

First, our Eldritch Blasts:

We have a +8 to hit, and we deal 1d10+4, or 9.5 average, on each of two hits, adding 1d10, or 5.5 average, on a crit. Thus, against the Wyvern's we hit on a 6 or higher, meaning a 75% hit chance. So, 75% of 9.5 is 7.125 and 5.5x5% is .275, so we get 7.4 average damage per blast, and thus 14.8 from this cantrip.

Next, our Vestige. We use a bonus action to command it to attack once. It also has a +8 to hit, and deals 1d6+7 on a hit (average 10.5) and an extra 3.5 average on a crit. 75%x10.5 is 7.875 and 5%x3.5 is .175, so we get 8.05 from the Vestige.

Then, we have our Battle Familiar, which does 2 attacks that hit for 1d8+8 per hit (12.5 average) and 4.5 extra on a crit. 75%x12.5 is 9.375, and 4.5x5% is .225, so we get 9.6 average per hit, and thus 19.2 average damage per turn from the spell.

Finally, we've got Summon Undead. The skeletal form does 2d4+8 damage on a hit (13 average) and 5 extra average on a crit. 75%x13 is 9.75, and 5x5% is .25, so that's a nice clean 10 damage per attack, and with two attacks, we've got 20.

Add it all up, and we're looking at 62.05 damage per round. Hey, when you're making seven attacks a turn, it adds up!

Now, if we get caught unaware, and still want to commit to this strategy, we basically need to layer things in the following way:

Turn 1: Cast Summon Undead and then bonus action command the Vestige. This means 28.05 damage on the first turn.

Turn 2: Cast Battle Familiar and then bonus action command the Vestige, which brings us to 47.25 damage on the second turn.

Turn 3: Eldritch Blast away and then command the vestige, doing our full 62.05.

    Now, the subclass, I think, is mainly giving us utility. That 8.05 extra damage isn't nothing: it brings this up to "really good" instead of just "pretty good" damage. But you can pull this off with other subclasses and do quite well. I'll also say that you might consider Summon Fey instead of Undead if you're going for maximized damage.

Still, it goes to show you that you can put out some big numbers here.

Simulating the GOO-Lock with a More Forgiving Target

 So, I'm at a crossroads here:

After a series of "vs Death Knight" simulations, I realized that while it's a cool boss monsters, it's also a very unusual target for a 10th level character. In my post about my Staff-and-Board Eldritch Knight build, I instead used a Wyvern, which simplifies things by being a non-legendary creature with no damage resistance or immunities and also has an AC closer to the average monster that you'd be fighting at level 10.

But it bugs me that its AC is 14, rather than 15. Is that insane? It doesn't have to be a really clean number (15 being a multiple of 5) but my OCD brain wonders if we should instead use a "target dummy" with a 15 AC and +3 to all saves.

Given that I'm revisiting a build here but figuring out its best damage output against a more reasonable target, I want to make sure I'm using the most reasonable target, in part so that I can compare this with other builds in the future.

But maybe a Wyvern is fine.

Hey, we've already done one that uses a Wyvern.

Ok.

I think what we can expect here is that the build will do significantly better because of the lower AC. We focused primarily on Eldritch Blast and Summon Aberration, though there are some questions as to what concentration spell might be a better choice. While Warlocks get the most Summon spells after Wizards (I think they don't get Summon Construct, which I believe is just Wizard and Artificer) one frustrating thing is that, because of the scaling of Pact Magic, we're never casting them at an ideal spell level - upcasting from 4th to 5th level only winds up adding a total of two damage if both attacks hit, so on any other class, you'd basically never want to cast these at odd levels unless you were desperate for their utility.

A GOO-Lock isn't obligated to cast Summon Aberration over other Summon spells, at least until Create Thrall comes at level 14. But given that these spells have expensive material components and you get this one anyway, I'd assume that Great Old One Warlocks are going to tend toward the Aberration.

There are interesting questions as to which aberration is the ideal one to summon. Beholderkin are probably the safest, given that they use a ranged attack and can also fly to stay outside of foes' melee ranges (though a Wyvern could go after them). However, Slaadi do slightly more damage (it's Slashing, but that's less of a problem in 5.5 than it was in 5.0) and have a health-regeneration effect that makes them basically fresh if they survive a combat and you have another one within the hour. Unlike the Skeletal Spirit from Summon Undead, Beholderkin aren't penalized in HP, though. Finally, the Mind Flayer (formerly Star Spawn) actually have the highest damage potential because of Whispering Aura.

Now, against a Death Knight, I'd generally thought that we'd be too scared that our Mind Flayer would just be smacked down immediately. But against a Wyvern, they might last a little longer. For a summoned creature to get swatted down by an enemy is arguably also good for the party, because it means those attacks didn't come for you or your allies - it just means that our damage output goes down.

Cast at 5th level, our Mind Flayer would have 50 Hp and an AC of 16. A Wyvern has a +7 to hit and across its two attacks does 48 damage. So, yeah, two hits could potentially take our guy out, though the chance of hitting twice on a single turn is only 36%, meaning that it's more likely than not that the Mind Flayer can survive a turn with a Wyvern focusing it down (though not much more than that).

So, how much damage are we getting from Whispering Aura? Notably, we need to position our minion at least 10 feet away from our allies to avoid catching them in it (it's not an optional pulse of damage), though we could also hit a rider with it. If we assume we're taking General Feats at 4 and 8, we'll only have a 19 to Charisma, so our DC is 16. A Wyvern will fail on a 14 or lower, so that's 70% of the time. The aura does 7 damage on average, so it's 4.9 average damage per turn. That's not insignificant, actually.

If we do a Beholderkin, the damage of its attacks are the same, but we don't get that 4.9 per turn. The Slaad hits a little harder.

Ok, we've got to do this whole thing:

Beholder and Mind Flayer attacks each do 1d8+3+spell's level, which means 1d8+8, or 12.5 on average per hit. With a +8 to hit, they'll hit a Wyvern on a 6 or higher, so 75% of the time. So, 12.5x75% is 9.375, and 4.5x5% is .225, so we get 9.6 damage per attack, and with two attacks, that's 19.2 damage.

Thus, the Beholderkin gives us 19.2 damage per turn and the Mind Flayer gives us 24.1.

The Slaad does 1d10+3+spell's level, or 13.5 average, with 5.5 more on a crit. 13.5x75% is 10.125, 5.5x5% is .275, so we get 10.4 per attack and thus 20.8 per turn.

Clearly the Mind Flayer wins, but only if we can keep it alive.

    As a note: my Great Old One Warlock, the very first character I came up with for D&D, has a patron who's less gooey tentacles and slime, and more akin to The Board from Control (though I came up with the concept before I played that game). It is a massive stone tower that is constantly crumbling and collapsing, but never actually falls - the Shattering Tower of Oedom-Het - and seems to occupy some strange place either in the Far Realm or on the Astral Plane. The point, though, is that I'd flavor each of these aberrations as more like inorganic (think stone or concrete) forms that have strange spatial anomalies as part of their anatomy. The Mind Flayer, I think, would be a vaguely humanoid form made of grey stone with a head that seems like a 4th-dimensional vortex projected into 3rd dimensional space, constantly shuddering and convulsing and projecting a cacophonous noise into the heads of those around them. Nothing about this creature seems organic, except for the smooth way that the vaguely humanoid body moves.

Again, we'll need to work to keep this thing alive, but we can actually calculate what the damage output would be with each of the options now.

Now, we're going to focus on Eldritch Blast as our primary source of damage (well, from us). At this level it's just two beams.

Real quick, though: I just wanted to see how True Strike compares. If we were to put our various invocations (including Agonizing Blast) on True Strike rather than Eldritch Blast, and we used a Light Crossbow (probably the most reasonable weapon for someone who only gets Simple Weapon proficiency if we're not going Pact of the Blade), at this level True Strike would hit for 1d8+1d6+4+4 (we're double-dipping on Charisma because True Strike already gets it). I think we can already tell that Eldritch Blast would do better, though, because if we combine both beams, that's 1d10+4+1d10+4.

So yeah, we're good.

Now, we need to consider Clairvoyant Combatant.

I skipped this on the Death Knight because it seemed very unlikely we could get it. But against a Wyvern, who has no legendary resistances, I think it's not unreasonable that we'd get this pretty useful feature to work.

We do need to get within 30 feet to activate it, but if it does work, we can open up as far as 4 miles (unlikely we will). However, we get just one free use per rest, after which we need to expend a Pact Slot to try again. I think this means we should probably assume we won't be trying it again if it fails - we'd rather keep the other slot in case we need to re-summon our minion or try something else.

It's a Wisdom save, so like the Mind Flayer's Whispering Aura, there's a 70% chance that it'll work, giving us advantage on our attacks. (The Mind Flayer won't benefit from this, so we don't need to change the math above).

Thus, we have advantage on our attacks 70% of the time, and not on 30% of the time.

Without advantage, we have a 75% chance to hit (just like our minion). Our hits will be 1d10+4, or 9.5 on average, with an extra 5.5 on a crit. 9.5x75% is 7.125, and (as we figured out earlier with the Slaad) 5.5x5% is .275, so that's 7.4 per Eldritch Blast, or 14.8 total at this level. However, the no-advantage roll is only 30% of the time, so that's really 4.44.

With advantage, that hit chance becomes 93.75%, and the crit chance is 9.75%. So, 9.5x93.75% is about 8.9, and 5.5x9.75% is about .54, so this is about 9.4 per EB and thus 18.8 total. This happens 70% of the time, so it's really 13.16.

Thus, our Eldritch Blasts do an average of 17.6 damage per round.

If we get our Aberration out before initiative is rolled, that will let us get that full damage each round, but I would guess that we'd typically have to wait a round.

So, we have three potential projections of damage-per-round based on our aberration choice.

With a Beholderkin, we do 36.8 damage per round (after the first if we didn't pre-cast).

With a Slaad, we do 38.4.

With a Mind Flayer, we do 41.7.

    So, there are fewer moving parts here than there are in my Eldritch Knight build, which did quite a lot more (especially if we assumed we could get their reaction strike), and I wonder if there are areas where I could tune up the build.

    Level 10 is a bit of a rough breakpoint for a Warlock, as they get a giant boost at level 11 with the progression of Eldritch Blast and the potential to pick up a more powerful spell (Summon Fiend, for example, will out-damage any of these 5th level Summon Aberration spells). In AoE situations, there's a good chance that Hunger of Hadar might be a better use of our spell slots and concentration, depending on how many targets it can get to.

But I'm not sure really how to boost the damage output here without using A: magic items or B: some weird multiclass build where we're not even sure we're a Warlock anymore (though Aberrant Sorcery is a pretty thematic thing to combine with this, even if there's a little overlap - but quickening Eldritch Blast can be pretty powerful). Apart from needing to close in for Clairvoyant Combatant, the lower damage of a pure-ranged strategy (using the Beholderkin) will allow us to stay a lot safer in combat.

Also, there are some fight-specific shenanigans we can get up to - if the wyverns have riders, maybe we can Repelling Blast them off their mounts?

We could get a fair amount of near-guaranteed damage by using Repelling Blast to shove them into a Hunger of Hadar - the Cold damage that the spell deals has no saving throw, so I'd put its upcasting scaling into that rather than the Acid. A Wyvern has a fly speed of 80 feet, though, so it might be hard to keep them in there, but against melee combatants with the standard 30 foot walking speed will have a harder time. Using Devil's Sight should, I think, let you see into it.

(Actually, unexpected rules nuance here: Darkvision doesn't actually prohibit seeing in magical darkness - it's the Darkness spell that says that. Hunger of Hadar explicitly says that no light inside the darkness can illuminate it, and that creatures fully within it are blinded, but technically nothing says that someone with Darkvision can't see into it from the outside. Devil's Sight, notably, is not Darkvision, but it does say you can see normally in darkness that is nonmagical or magical, so either should work here).

Screw It: Let's Optimize a Bladelock

 I have a love/hate relationship with the very idea of optimizing in D&D. I think the game works fine if you're just doing straightforward builds - even a Champion Fighter who does nothing but take ASIs will still... no, hold on, that's insane. Even a Devotion Paladin who takes nothing but ASIs will still perform just fine, and a party of simple, straightforward characters will be able to overcome the challenges balanced with the encounter math in the Dungeon Master's Guide. There might be some hairy situations here and there, but they'll probably be fine.

And I also think that optimization can sometimes come at the expense of immersing yourself in a character. Indeed, I think far worse than picking off-theme options to ensure your character is powerful, the worse thing is when you want to pick thematic choices that wind up sabotaging your character. Like, a Cleric/Paladin multiclass would make a ton of sense for a character who wants to live in the overlap between those classes, but the mechanics don't support it very well, splitting your spellcasting between two ability scores.

And yet...

I also think that with games that are lighter on rules, like my experience with Kids on Bikes, there's a certain flatness to them, where there's no real way to "play well" in a mechanical sense.

And maybe that's an unresolvable issue - a game that is perfectly balanced and allows you to pick any character options that is guaranteed to allow you to be just as effective as any other array of choices must sort of undercut the effectiveness of rules mastery and system analysis.

So, here I am, someone who really loves the potential for original storytelling in D&D, but also who really wants my numbers to be big.

And I think part of why there's an industry of optimization discourse online is that it's just something that can actually be calculated. While there's plenty of scholarship on what makes good storytelling work, it's also subjective, whereas you can back up an optimized build with math.

I wrote recently about comparing Warlocks that go with Pact of the Blade and really focus on fighting with a melee weapon versus a more "classic" Warlock that fights from afar, primarily using Eldritch Blast.

Perhaps moreso when 5E was new, but I do see a lot of people are drawn to the Warlock to play a kind of dark spellcaster, and wind up disappointed when they realize how limited the class is in terms of the amount of spellcasting you can do. I realized pretty early on, though, that the trick to the Warlock is to think of them not as a limited spellcaster, but as a very versatile martial class.

Any character in D&D can weaponize their magic, but a Warlock is one that really treats its magic (especially Eldritch Blast) as a weapon, and thus their gameplay in combat really resembles a martial character.

Pact of the Blade, then, makes that basically literal.

Now, I have generally been inclined more toward the "Blastlock" style of Warlock, and my very first character was built along those lines (though only made it to level 2, as it was for a limited campaign where my best friend was first trying out DMing - something he now does professionally). But I then played one in a Descent into Avernus game (yes, I played a Hexblade but did not go Pact of the Blade. Is that weird?)

So I do sort of feel like I'd want to go Bladelock just to do something new.

But beyond that, what kind of Bladelock do we want to be?

5.5 made a giant improvement to Pact of the Blade by allowing you to use Charisma as your ability to attack with that weapon. This had previously only been a feature for the Hexblade subclass, which made it the obvious option for any Bladelock.

But there are other issues.

Warlocks only gain access to Light Armor. Even if you are a Dex-based class like a Rogue or most Rangers, it takes a while to actually get a decent AC with light armor (I'd generally take medium armor instead on a Ranger). The best mundane light armor simply gives you an AC of 12+Dex, which means that capping it out will get you 17, and even for a Rogue that's not likely to happen until level 8 or even level 10 (when Rogues get their third feat). For Bards, Druids, and Warlocks, who are probably not going to be able to focus very much on Dex, even if they start off with a +3 to Dex, they're unlikely to be able to raise their AC above 15 or so until maybe level 16 (barring, of course, magic armor). Now, in the case of Bards, if you're playing a melee-focused Bard subclass, you typically get either medium armor training or unarmored defense. And Druids can pick the Warden Primal Order at level 1 to get medium armor training, or will get the new Moon Druid armor bonus when in their Wild Shape.

The Hexblade came with training in medium armor and shields along with martial weapon proficiency (the latter of which is irrelevant if we're getting Pact of the Blade). So, rather than struggling with an AC of, like 13 at level 1, you could very quickly get an AC of 16 or 18 (with a shield in the latter case).

For Blastlocks, this isn't as big of an issue - having a low AC as a ranged character isn't too bad because most of what comes at you from range are effects that call for saving throws, and you're generally playing around making sure that you keep some distance from foes that could hit you.

But the whole idea of a Bladelock is to be able to close in with your foes.

Sadly, there's not an obvious solution within the class itself (other than the Xanathar's version of the Hexblade, which is probably getting an update without any armor training in the Arcana Unleashed book). You could take Moderately Armored, though frustratingly, if you also wanted shield training, you'd have to also get Lightly Armored, half of which is redundant for you. These feats don't increase Charisma, so you'd also be penalizing your Charisma progression.

And furthermore, you're also probably going to want to pick up some kind of weapon-focused feat the increase your damage, which will also not improve your Charisma, so it's sort of extra costly.

Thus, as much of an improvement as the 5.5 Pact of the Blade is compared to the 5.0 version, I think that any reasonable build is going to do some multiclassing.

Boo! Hiss!

Yeah, I've said many times that I am not a fan of multiclassing. I love subclasses that can incorporate elements of another class into your class to give you that kind of hybrid identity, like the Eldritch Knight as the "Wizard-like Fighter," but I think multiclassing can melt down class identities.

But just to make a Bladelock build work, it's just so effective at fixing some of these issues that it's hard to pass up.

Now, how and what to multiclass into?

As I see it, one of the top priorities is to get something with some armor training. While a Sorcerer/Warlock build can work fantastically, that's going to be great if you are really focusing on spells. We'd want to grab something with either medium or heavy armor training, but I'd also say we probably don't want to introduce any more ability requirements, especially as we're already going to be stretched a little thin.

Thus, I think that the Fighter and the Paladin are the clear best options here.

Let's talk about why for each:

First off, both give you Medium and Heavy armor training - though the latter only if you start off with that class. Weirdly, the only class that can give you Heavy Armor with a single-level dip after you've already started with Warlocks is the Cleric, thanks to the Divine Order choice, but that would also mean we'd be splitting our spellcasting between Charisma and Wisdom.

If we're fine with just Medium armor, then it's ok, but I think we're going to want to get Heavy armor instead for two main reasons:

One is that it just caps out a little higher, letting us get an AC of 18 with just mundane equipment (or 20 if we have a shield). But more importantly, we need to figure out our weapon choice.

As I see it, melee builds in 5.5 are going to want to grab one of four feats: Dual Wielder, Great Weapon Master, Polearm Master, or Shield Master (actually, Grappler is another possibility, though I think that's not going to be one that Warlocks pick). Dual Wielder isn't going to work for us, because we only get the one Pact Weapon, and even if we get a great off-hand weapon, we won't be able to bond with it to make our attacks with Charisma. So we really want to focus on a single weapon.

Shield Master is also questionable. First off, we don't inherently get Shield training, though again, we're assuming starting with a level of Fighter or Paladin, so we will get it. But its Shield Bash option scales only with Strength. That actually might not be a terrible problem because we're actually going to likely be getting our Strength reasonably high anyway, but I think we've got some other options that can be better.

Great Weapon Master, generally when I've calculated things, gives you the most overall damage for any martial build. Given the nerf to Sharpshooter in 5.5, it's even a pretty good thing to take on a ranged martial build.

However, Polearm Master is also a very solid, and importantly, a very versatile feat to build around. While I usually think of builds with this feat as using just those d10 heavy reach weapons, both of its components (Pole Strike and Reactive Strike) actually work just as well with Spears and Quarterstaves. While none such weapons are Finesse weapons, you can also choose to boost your Dexterity with this feat. I assume that's to make it usable with Monks (though the Pole Strike feature is less exciting for a Monk who always gets a bonus action attack anyway).

Still, if we want to take Great Weapon Master (which I do think still gives the most damage of all of these) you'll need a minimum 13 in Strength. Pushing Strength and using Heavy Armor will then allow you to worry less about Dex as you can get a decent AC without it. Now, this also commits us a bit - Chain Mail won't slow you down if you have a 13 or higher Strength, but to move unimpeded with Splint or Plate, you need 15.

If you do want to go this route, then, you might consider starting off with a 14 in Strength (either taking it with Point Buy or using a background that lets you get there from 13) so that simply taking Great Weapon Master will get you to the place where you can wear any heavy armor and you'll never have to worry about it again (though if you also hate having odd-numbered ability scores, you might consider rounding that out after you've capped you Charisma later on).

Something you'll get from both classes as well is Weapon Mastery. Generally, I think Graze beats just about all other options, but having Cleave or Topple or Push can be great as well. As good as Graze is, it's not something you need to build around like Nick, so if your DM gives the party a really awesome Greataxe, you can still feel comfortable taking it.

Now, between Fighter and Paladin, which is the one to go with?

I think there are good arguments for both, but I'll say this: it's going to be pretty hard to resist putting several levels into Paladin. Aura of Protection is among the best class features in the game, and as a Charisma-focused character, it'll be even better for us than it would be for a traditional Paladin who might not have more than a +3 to Charisma until tier 3.

Depending on how far your campaign goes, this might mean that you wind up being more of a Paladin than a Warlock. Now, you don't have to do this - you could just grab a single level to get the armor training and such, and then have two more spell slots that you can use on spells that don't scale all that well.

For Fighters, it's a bit easier to just do a single-level dip. One of the big things here is that you'll get here is a change to your saving throw proficiencies (Warlocks and Paladins I believe get the same ones, Wisdom and Charisma). By getting Con save proficiency, you'll be protecting your concentration spells, which will be precious given how few spell slots you have. Also, with just one dip, you'll already get a Fighting Style feat. I actually think that the Great Weapon Fighting style is pretty bad compared to what dual-wielders or sword-and-board people can get, but you can also pick up something like Defensive to just be a bit harder to hit, or Blindsight (though this is less exciting if we get Devil's Sight). Interception is actually great, and doesn't require you to specifically have a shield like Protection does.

Now, I think eventually getting a second level of Fighter to pick up Action Surge is probably worth it eventually, but it's also pretty easy to just dip in once and then focus on Warlocking it up.

Notably, because Pact Magic and Spellcasting are different features, the spellcasting of a Paladin doesn't actually help at all with your spellcasting progression as a Warlock, which I think moves the needle a little away from them.

And lastly, picking either class first is going to give you a tiny bonus to your max HP. At level 1, you'll have 10+Con, whereas a Warlock will get just 8+Con. Taking average rolls, subsequent levels of Warlocks will give you 5+Con while levels of Paladin or Fighter give you 6+Con, meaning that by starting off Fighter/Paladin, you get 1 more HP!

    Ok, but now that we've made a truly foul bargain with the mysterious entities behind the mechanical design of the game (multiclassing is the true devil's bargain we take for power,) we're going to commit to Warlock.

Obviously, at level 1, our biggest decision to make is that first Eldritch Invocation, and the whole point of this was to go Pact of the Blade. So that's what we do.

For spells, honestly, I don't think any of this is going to be very shocking. We'll still want Eldritch Blast because it's nice to have a ranged option. We actually don't really want to pick up Booming Blade or Green-Flame Blade because eventually we'll do more damage just by attacking multiple times.

As much as I complain about Hex, it's still going to be great at this level and for a little while to come. Armor of Agathys is also good, though it's less exciting at 1st level, as it can be wiped out by a single attack pretty easily.

Broadly speaking, I'd then try to stick to Warlock until we're level 12 - Fighter 1/Warlock 11.

We have several Invocations that are basically non-negotiable. Thirsting Blade will come at level 6 (Warlock 5) and give us Extra Attack. That does mean that while our full Fighter/Paladin/Monk/Barbarian/Ranger friends are getting their second attack, we'll be sadly crying in the corner with the Rogue. However, just like Valor Bards and Bladesinger Wizards, we'll then get that extra attack a single level later (sorry Rogues). Then, at Warlock 11, we'll take Devouring Blade, which gives us a third attack, which is huge.

Other less mandatory but still interesting options are Eldritch Smite, which lets us use a Pact Slot to add 1d8 force damage for each level of the spell slot. Notably, this didn't get turned into a bonus action or count as casting a spell, unlike Divine Smite. I would still save this for crits, though. Lifedrinker is ok, giving us an extra d6 of damage per turn and potentially let us do some emergency healing, though it won't scale with our attacks, unfortunately.

For spells, there's kind of an interesting question:

I do like Spirit Shroud, which lets us add a d8 of damage to each of our hits, and scales up to 2d8 when we have 5th level slots. Once we have Devouring Blade, that can mean an extra 6d8 damage per turn (around 27 average). It is for sure more damage than Hex (though it doesn't last as long). However, a Summon spell can potentially get you some more. At 5th level, a Summon Undead spell with, say, the Skeletal Spirit, will get you two attacks that each do 2d4+8, which is slightly less. Summon Fey requires you minion to get into melee, but it can deal 2d6+8, which winds up being a little more.

However, if we do get to 11 levels in Warlock, we can pick up Summon Fiend. Unfortunately, we can't just upcast any of our 1-5 spells any higher, but as a natively 6th level spell, Summon Fiend will give us a fiend that gets to make three attacks. The Devil version hits for 2d6+9 on three attacks, meaning potential damage of 48 damage per turn, which is going to do better than we can with Spirit Shroud.

The downside to these spells, of course, is that you need to protect both your concentration and your minion's HP. But I think particularly the Skeletal Undead, the Beholderkin Aberration, and the Devil Fiend are solid options here because they can stand at pretty far range (the Beholderkin and Devil can also fly and thus stay away from melee-oriented monsters).

Pretty much any spell that any Warlock would like will work with a Bladelock, but apart from Spirit Shroud, are there any that really reinforce the melee combatant toolkit? The truth is... not really? Armor of Agathys, which by the time you can cast it at level 5, is going to be pretty sweet, and probably net you 50 damage or more (if you have a way to recharge your Temp HP, that can extend the life and thus the damage of that spell). 

Ok, so what about subclasses?

Archfey's emphasis on Misty Step will certainly help you be a bit more of a "hit and run" melee combatant, allowing you to A: get away from foes when you get into trouble and B: get to far-away foes.

Celestial honestly doesn't offer a ton that's melee-specific. It's thematically cool if you are multiclassing with Paladin, of course, and the healing can help with the fact that you're probably taking more damage.

Fiend has a pretty big survivability feature in Dark One's Blessing (remember when I mentioned Armor of Agathys being better if you can recharge your Temp HP?) And if you get 10 levels, you could potentially give yourself resistance to one of the common melee types of damage (though you have to kind of guess if you're more likely to encounter bludgeoning, piercing, or slashing damage). Fiend does get Scorching Ray, which will scale very well with something like Spirit Shroud, but doesn't, you know, really help with our melee theme.

Great Old One sort of encourages you to get closer to your enemies for Clairvoyant Combatant, though only with 30 feet (and I think if it works, you can then back off. Still, if you can give a foe disadvantage on all attacks against you while you get advantage, that's pretty nice.

Undead (which is the one I'd do a Bladelock with, mainly for thematic/aesthetic reasons) gives you some extra Temp Hp with Form of Dread, and the ability to frighten foes can also effectively improve your survivability and give you some battlefield control. Thanks to the fact that your Pact Blade can do Necrotic damage, you can thus apply the Dreaded Necrosis bonus from Grave Touched to your weapon attacks. This might make you consider a Greataxe to get a full extra d12 each turn rather than just another d6.

    What Does This Get You?

The real question here is this: do you wind up being more powerful than a normal martial character?

I think the answer is probably "maybe a little." Indeed, a lot of what we're doing with the build is kind of just making sure we can do with Charisma what a comparable Fighter would do with Strength. We do have various magical abilities, which inherently give us a bit more versatility. But we're not going to be the grand toolbox that is a Wizard or the damage-dealing powerhouse that is the Sorcerer.

But I also think you'll hold your own decently. I'm sure there are some more narrowly optimized builds out there that can squeeze a ton out the class, but outside of dipping into more classes and further-deemphasizing the Warlock of it all (and I don't even know what specifically I'd do to get that) I think this is about all I can figure out at this point.

Taking the build past level 12, I think it's actually a pretty reasonable breakpoint where we could consider going outside of Warlock again. Maybe one more level in Warlock to get the feat at level 12, though putting another 5 in Fighter will get us two additional feats along with unlocking a subclass for the Fighter. In fact, if we went Eldritch Knight and put a full six more levels (this would have us at level 18 at this point, so that's pretty high up) we could get War Magic and start weaving in either Booming Blade or Green-Flame Blade, or even starting off with an Eldritch Blast and then making two more attacks, and then we could Action Surge for another Eldritch Blast and two attacks because we'd be casting it as part of the Attack Action rather than the Magic Action and thus get around the restriction on Action Surge. That means that, yes, again, at level 18, we'd be able to effectively make 12 attacks in a single turn (which would make that Spirit Shroud scaling start to look real good) and even after we Action Surge, we could still do 6 per turn (we might want Spell Sniper to ensure we can cast in melee without problems, though if we start using a Glaive or other Heavy Reach weapon we could try to always stay exactly 10 feet away).

Bladelock vs. Blastlock in 5.5

 While the design has tried to open up other options if you so choose, I really think that a pure-caster Warlock truly ought to go with Eldritch Blast. There's a reason why they make this cantrip so good and give it solely to a class that, for a spellcaster, is much more reliant on cantrips due to the limited nature of Pact Magic.

But they've also taken some steps to make a weapon-focused Warlock more viable in 5.5 (not counting the way that the Hexblade subclass already solved a lot of these issues in Xanathar's). The question, though, that I've always had is this: is going Bladelock actually worth it?

First, I want to touch on raw damage:

Eldritch Blast does a d10 of Force damage, the most reliable damage type in the game, and unlike Fire Bolt, which is also a d10 cantrip, it splits the damage into multiple blasts at each tier of play. In a vacuum, this doesn't actually change anything other than kind of smoothing out hits and misses and crits. But quite early on in a Warlock's career, they can get various things that make this a pretty important element: Agonizing Blast allows you to add your Charisma modifier to the damage of Eldritch Blast, or of a chosen alternative cantrip. But if we were to put this on, say, Mind Sliver, we'd still only be adding that Charisma modifier once even if we've upgraded to 4d6 damage from the cantrip at level 17. Eldritch Blast, though, multiplies this benefit across its multiple beams from level 5 onward. The same is true for the Hex spell, which adds a d6 of Necrotic damage to each individual hit.

The upshot of this is that Eldritch Blast actually winds up working more like a martial character's weapon attacks. I believe the Heavy Crossbow has the Push mastery, so a Fighter using that (and Crossbow Expert to actually benefit from extra attack) is going to be hitting for 1d10+Dex and pushing a target back 10 feet with each hit, while a Warlock with Agonizing Blast and Repelling Blast is going to be doing 1d10+Cha and pushing a target back 10 feet with each hit. At level 5, that's going to be twice, and then at level 11, both will be hitting three times.

Now, a d10 is among the highest native damage dice for a weapon type - only d12 weapons (Muskets and Greataxes) and 2d6 weapons (Greatswords and Mauls) do more (until we get into the Modern/Futuristic Firearms, which are not considered standard equipment).

In other words, at this basic level, Eldritch Blast is quite good. So, what are the advantages of going Pact of the Blade?

Initially, there's a bit of a limitation with Pact of the Blade, because it's limited to melee weapons. That said, if you get your hands on a magical ranged weapon, it will also work with it as well. Thus, a Warlock could use a Repeating Heavy Crossbow just fine.

In 5.0, though, leaning into a Blade Pact presented a challenge, because it didn't change the ability modifier you used with the weapon. Essentially, you were opting into being Multi-Ability-Score-Dependent (or MAD) or just letting Charisma stagnate and just picking spells that weren't reliant on a good spell save DC or attack bonus. There are such spells, to be clear, and I'd generally recommend that with a lot of magic/melee hybrids that you try to pick spells that don't really need a high spellcasting ability (my Eldritch Knight used Booming Blade and Green-Flame Blade, and Shield as his primary spells, none of which care what your Intelligence is).

One of the (several) things that made the Hexblade patron (consider Ebonbane or Nepenthe, two evil sword Darklords, as patrons!) so popular especially for Bladelocks was that it allowed you to use Charisma to attack with your Hex Weapon, as well as any weapons you had bonded to with Pact of the Blade, so you could simply worry about having enough Dexterity to max out your Medium Armor (another huge benefit the subclass gave) and then just focus on Charisma.

But this brings us back to the question: is a weapon really better than Eldritch Blast?

The answer is... it can be.

Let's again address raw damage: if you take a Greataxe, Maul, or Greatsword (or a magical Musket), the damage is going to be a little higher than Eldritch Blast. Each hit with a Greataxe is going to do on average 1 higher damage from the dice than Eldritch Blast, and the 2d6 weapons are going to hit for 1.5 higher damage.

Next, there's the issue of magical damage boosts: spellcasters can get Wands of the War Mage, or for Warlocks specifically you can get Rod of the Pact Keeper, which give you a bonus to attack rolls (and for the Rod, also spell save DCs) from 1 to 3. However, these don't add to the damage of your spells. Thus, a Blastlock using a +2 Rod of the Pact Keeper is still only going to hit for 1d10+Cha with their Eldritch Blast hits (again, we're always assuming you get Agonizing Blast, probably right away at level 2). By contrast, a Bladelock with a +2 Greatsword is going to be hitting for 2d6+2+Cha with each hit. At 5 Charisma, that's an average of 10.5 versus 14. Likewise, if you can get your hands on a Vicious or Flametongue weapon, this starts to really take off quite a bit.

Now, concentration spells are, I think, a bit of a wash: if we assume a Bladelock is taking Thirsting Blade at 5 and Devouring Blade at 11, the number of attacks they get to make keeps pace with Eldritch Blast. Also, most spells that increase the damage of Eldritch Blast, like Hex or Spirit Shroud, will also increase the damage done by a Pact Weapon, so that's a wash as well. This does fall off at level 17 - here, Eldritch Blast starts to shoot 4 beams, while there's no Eldritch Invocation to get four attacks with our weapons (which would really step on the toes of Fighters' capstone).

However, we also need to talk about Feats. Martial characters have a number of good feats that they can take to significantly increase the damage they deal. The most powerful of these, according to math I did back when the 2024 PHB came out, is Great Weapon Master, which allows you to add your Proficiency bonus to the damage of heavy weapons when you take the Attack Action, as well as letting you get an extra bonus action attack if you either crit or take an enemy down (the latter of which is harder to calculate because it's very situational). Still, the PB bonus both scales as you level up and also scales with the number of attacks you can do, is pretty great for a Warlock who is eventually going to get 3 attacks per Attack Action.

Eldritch Blast is going to basically cap out in damage with four beams that hit for 1d10+5 (again, ignoring spells and such that boost our damage). That's 42 damage on average. A Bladelock using a Greatsword will cap out at three attacks, but those attacks with just a +1 Weapon and Great Weapon Master, will be doing 2d6+1+5+6 at level 17, or 19 damage per hit, meaning 57 damage. Add on, say, a 5th level Spirit Shroud doing 2d8 extra damage on each of those, and you're adding in 36 for the Blastlock (though they have to be pretty close to the target) versus 27 for the Bladelock, which gives Blastlocks 78 versus Bladelocks getting 84.

So, I think we can say pretty confidently that, at least if we're just doing straightforward damage-dealing and damage-boosting, Bladelocks are going to have the edge.

Another thing to note here is that a Bladelock can still pretty easily pick up Eldritch Blast and even fit in Agonizing Blast among the Invocations (they'll have a couple to pick at early levels before they can get Thristing Blade). So a Bladelock can still largely play like a Blastlock as well.

Does that mean everyone should go Bladelock, then?

Naturally, you don't need to play everything perfectly optimized. Indeed, sometimes I wonder if doing math like this is a curse, revealing knowledge that I'd rather not have because I think it's generally best to build a character in this game around the story of the character. I actually appreciate efforts by games like Draw Steel to sort of "auto-optimize" your character so you can just pick the thematic options (though I also have less of a sense of how actually balanced the game is, even if it seems pretty balanced from the outside).

But if you're hoping to maximize your damage output, yeah, probably. But let's talk pitfalls:

One of the big weaknesses that a Warlock has is that you only get Light Armor. If you're a ranged character, this isn't that much of a big deal: threats from range tend to be based on saving throws rather than attack rolls (though not exclusively) and so having a low AC isn't really that much of a problem if you're staying out of melee range. Bladelocks don't have that luxury. Given that you probably don't want to do anything with your Dexterity until you've capped your Charisma, mundane Studded Leather is probably going to keep you at an AC of like 15 max for most of your adventuring career. In my experience, DMs are often hesitant to hand out magic armor, which maybe we should be more generous with - but even +3 Studded Leather is going to get you like 18 AC, which a level 1 Paladin can start out with.)

Next, if we do want to use Great Weapon Master, we're going to need a minimum of 13 Strength, which is just high enough to mean we can't really push Charisma, Dexterity, and Constitution all up to chunky levels. Polearm Master actually allows for you to push Dex, but unless you get that 13 Strength to use heavy melee weapons, you'll be limited to Quarterstaves and Spears, which, even two-handed are going to do less damage than Eldritch Blast (I honestly often forget that this feat works with those types of weapons).

Generally, my solution is to take a single-level of Fighter to start off with. This actually solves a ton of different problems for a Bladelock, giving you access to Heavy and Medium Armor, as well as Weapon Masteries, and even gives you proficiency in Con saves. I've had, for a while, a concept for an Undead Warlock whose patron is an entire chivalric order of Death Knights, and I think that's a concept that works particularly well for a Bladelock. But you pay the Multiclass tax there. It delays features, such as having to wait until level 6 for Thirsting Blade and level 12 for Devouring Blade, as well as delaying your higher-level spells (even if you instead multiclass with Paladin, the separate scaling of Spellcasting and Pact Magic means that you're still not getting those higher level spells or spell slots as soon).

But I think trying to pick up, say Heavily Armored and then Weapon Master on top of Great Weapon Master would be more of a burden than this single-level investment.

Essentially, if you want to straight-class a Warlock, there's very little friction for a Blastlock to go that route, while a Bladelock is going to need to plan things out a bit more carefully.

I will also say that when I did my "vs. Death Knight" simulation, I wasn't terribly impressed with the Bladelock's performance, though I do think it outdamaged my GOO-Blastlock (I also think I should start doing these simulations against creatures without legendary resistances, necrotic immunity, and such high ACs).

Undead Warlock vs. Death Knight

 First off, we're taking a little departure with this one: this is a multiclass build. For me, I think there's just such amazing utility to starting with one level of Fighter if you want to go Bladelock that I can't really justify not doing it.

But I need a story to justify it. I had previously built this character with the 5.0 version of the subclass and not even really a Bladelock. Our hero (more of an antihero) was a courtier in a lofty hall of a nobleman, but when treacherous fey visitors turned on his childhood friend/liege lord and slaughtered everyone in the manor, he was walled up Casque of Amontillado-style in one of the walls of the basement. There, he suffocated to death and was caught in a liminal void for countless years, until a mysterious voice contacted him, instilling life into him once more as a Reborn. Emerging from the haunted ruins of the manor in which he had done his life's work, he followed the directions of the voice to a ruined tower, and therein, he found an entire knightly order that had been corrupted into undeath by those same treacherous fey, and cursed to never leave their tower. The knights offered to imbue him with power if he would act as their agent in the world, and thus he became a Warlock.

The tweak to the story is that, likely rather than a pure bureaucratic functionary, he was likely a member of some kind of honor-guard for his friend, hence beginning as a Fighter.

With that out of the way:

Something about the Undead patron to me feels particularly good for a Bladelock - while you could certainly fight in the name of a Demon Lord or an angelic avenger (actually, a "thornblade" for a coven of hags sounds cool too) I've always loved Death Knights (WoW is a big reason why) and it seems like a servant of Death Knights really ought to be more martial in nature.

    Classes:

We're trying to lean as hard into Warlock as possible. Once we secure Devouring Blade at level 12 (Fighter 1/Warlock 11) we might consider putting a bit more into Fighter to get Action Surge and a subclass, but that's outside of our purview right now.

The single level of Fighter does the following for us, though:

We get Weapon Masteries, including Graze, which will be the one we benefit from the most.

We get Medium and Heavy Armor Training. We're actually going to lean toward heavy armor because we'll need a reasonable Strength for both the Heavy weapons we want to use and the feat we'll want to take at Warlock 4.

We also get Con save proficiency, which will help us with concentration.

Once we have that first level, we're going to pour everything into Warlock, and stick with it for the rest of this 10-level build.

    Stats:

Primarily, we want to start with a 17 in Charisma and a 13 in Strength, and then try to get a decent Con - I don't typically like to dump more than one stat, so you're probably getting a 14 in Con.

    Invocations:

We're going to take most of the Blade-focused Invocations we can here. Pact of the Blade naturally at Warlock 1, and then Thirsting Blade and Eldritch Smite at Warlock 5. We'll also grab Devil's Sight, partially because Reborn don't get Darkvision, but even with other species, this lets us do Darkness shenanigans. Lifedrinker is a possibility, but I'm skipping it in favor of Lessons of the First Ones to take Tough and bolster our HP - we need to split ourselves a little between Strength, Charisma, and Con, so this will make up for both our mostly d8s of hit dice and probably not getting more than a +2 to Con. Tough effectively makes our hit dice d12s for the purpose of calculating our max HP. Finally, we'll grab Pact of the Chain as well, getting a nicely flavorful Skeleton familiar, though even though we can use them in combat, we probably won't. I'm also taking Agonizing Blast so that we can still use Eldritch Blast as a ranged option when we need to.

    Gear:

Thanks to starting as a Fighter, we'll start off with Chain Mail. Now, one thing we have to deal with is that we actually will be slowed if we take Splint or Plate, because we're not going to have more than a 14 in Strength, at least until much later in our careers. If we can get better, magic Chain Mail, that'll be great, even if it only gives us the AC of Splint or Plate.

We're going to stick with a Greatsword as our main weapon - I don't think we'll have the feats to invest in both Great Weapon Master and Polearm Master, as we'll still want to take Charisma-boosting options after level 4. That's fine, these hit very hard and have Graze.

    Feats:

We're going to grab Great Weapon Master at level 4, which will boost our Strength to 14.

    Spells:

Ok, now for the big one:

We only have two Pact slots at level 10, but they're both 5th level.

The main spells I'd focus on using are Spirit Shroud and Armor of Agathys.

Both use a bonus action to cast, one providing a bit of damage along with some resilience, and the other boosting our damage. Thanks to Tough and our armor, we should be a fair amount more resilient than your typical Warlock. Agathys is great, and in theory we can even refresh its Temp HP with Form of Dread, though against a Death Knight (maybe even one of our patrons?) its effects won't be that useful aside form the Temp HP.

Given that we have Thirsting Blade, we won't be using spells like Green-Flame Blade or Booming Blade. Again, I'd grab Eldritch Blast for a ranged option, but the rest would probably be more utility spells.

    Attack Sequence:

With our pact Greatsword in hand (doing either psychic or radiant damage - necrotic is no-go against a Death Knight) we're going to start off by casting Spirit Shroud. At 5th level, this will add 2d8 to each of our attacks, doing our choice of radiant, necrotic, or cold damage (we'll go radiant again). It's similar to Conjure Minor Elementals, but has worse damage scaling but only takes a bonus action to cast. Given how OP CME is, I think that still means this is a very solid spell. Also, CME isn't a Warlock spell.

We probably want to save our remaining spell slot to either re-up Spirit Shroud or use it on a crit for Eldritch Smite. At 5th level, Eldritch Smite does 6d8 damage, but we can make up for that if we hit three times with Spirit Shroud. But a crit would make it very worth to blast out some insane damage. Armor of Agathys could be an option if we are worried about survivability - it can also put out a lot of damage to attackers when cast at this level, but you need to hope that the Death Knight rolls low damage.

Notably, as Reborn, we might have Necrotic resistance, which would be great in a fight like this, but we also probably aren't taking it because we will get that anyway for being a 10th level Undead warlock.

    Damage Output:

Notably, we only have a +4 to Charisma, so we're not going to be hitting quite as often. That said, Graze is going to help us out a lot. The calculation is actually quite simple, as ultimately we're just making two attacks that are buffed up.

With Spirit Shroud up, we're now dealing 2d6+2d8+4 radiant damage per hit, so that's 20 damage on average, with 16 more on a crit. That said, because we have Graze, we can actually just guarantee the 4 and throw the hit and crit damage together.

With a +8 to hit, we'll land an attack on a roll of 12 or higher, so 45% of the time. Add in the 5% chance of a crit, and you get 50% of 16, or 8, and then add in the guaranteed 4 each turn to get us 12 damage per attack, or 24 damage per turn.

If we do land a crit, we will be adding 12d8, or about 54 damage on average.

Still, I'm honestly a little surprised at how underwhelming this damage is.

Oh! I forgot Great Weapon Master!

So, let's rewind:

We're actually now hitting for 2d6+2d8+4+4 on a hit, or 24 on average, and adding 16 on a crit.

Again, we're going to pull 4 out of that and add it in later for Graze, so we'll look at 20 damage on a hit.

20x45% is 9 (such round numbers!) and 5% times 16 is .8, so it's really 9.8, and then adding in the guaranteed 4 to give us 13.8 per attack, which gives us 27.6 damage per round. Certainly a bit better, but still a little underwhelming.

However, while we've used our bonus action on this turn to cast Spirit Shroud, on subsequent turns, we will get to make a Hew attack if we land a crit. With two attacks, the chance that happens is 9.75%.

Without the extra 4 from GWM, we're going to do 12 average damage on an attack (as we calculated before, ) so in the 9.75% of the time we get to do this, we're adding 1.17 damage per round, bringing us up to 28.77, which still feels pretty low.

    Ok, so we're switching our gameplan:

We're basically a Death Knight ourselves. And what does a Death Knight have? An army of skeletons.

If we assume we can find a whole bunch of bones, we're going to cast Danse Macabre, ideally before combat. We raise 5 Skeletons, and each skeleton is going to get a bonus equal to our Charisma modifier to their attack and damage rolls. This winds up actually giving them a +9 to hit, and their attacks (probably using bows to avoid being too close to the Death Knight) deal 1d6+7 damage on a hit.

If we can't cast ahead of time, we'll do this at the start of combat and immediately have them attack.

Each has a 50% chance to hit. 1d6+7 is an average of 10.5 damage, and they do an extra 3.5 on a crit. So that's 5.25 plus .175, or 5.425 damage per attack. There are five of them, so with our bonus action to command them, we're doing an average of 27.125 (already basically outpacing our previous plan).

Now, our bonus action is now spoken for, so we're just making our two melee attacks on our turn, and this time without Spirit Shroud. So, we'll deal 2d6+8 on a hit and add 2d6 on a crit, or 11 and 7. We can remove 4 guaranteed damage and calculate 11x45%, or 4.95 and then the 7x5%, or .35, for 5.3, add in the guaranteed 4 for Graze and we get 9.3 damage per attack, or 18.6 damage from us if we don't need to spend our action on Danse Macabre.

Thus, our damage becomes 45.725 and holy moly that's freaking incredible.

Two notes, one good and one bad.

The good note is that we actually don't need our bonus action after the first command if the command is simply "keep shooting at the Death Knight and spread out while staying in regular range with your shortbows," as the skeletons should continue to follow a command until it's completed. Thus, we can now get our Hew attacks in if we get them.

The bad note is that the Skeletons are going to be very fragile - the spell doesn't boost their survivability at all, and so they're prime targets to be wiped out by Hellfire Orb. Keep them spread out as much as you can to avoid losing too many to one.

Danse Macabre was a fun spell introduced in Xanathar's, but it mostly wasn't as good at higher levels when you started fighting monsters with resistance or even immunity to nonmagical weapon damage. But as that as a concept has been excised from 5.5, spells like this have gotten way better.

You will need to find corpses to animate - you can also make zombies with it, but skeletons are much better damage-dealers - but hopefully with a Death Knight you'll have plenty of bones around (though it's also unlikely that those bones are all inert).

Spirit Shroud will get a bit better when you can get 11 levels in Warlock and grab Devouring Blade (you might consider using it with Eldritch Blast when you are Fighter1/Warlock10, as EB will upgrade its number of beams a level earlier). But if you can keep those skeletal archers alive, Danse Macabre is honestly a really good source of damage.

Undead Patron Warlock (Horrors Within)

 This is one of my favorite subclasses. An undead warlock patron has always felt like a no-brainer, and after the really underwhelming Undying patron from SCAG (which wasn't even necessarily undead) the true, full Undead patron that we got in Van Richten's became one of my favorite Warlock subclasses instantly.

Warlock subclasses got one major change in 5.5, giving them all of the spells associated with their subclass rather than merely expanding their options. Notably, this does also mean that sometimes your Patron spells will be spells you could have taken anyway.

Many a Darklord could serve quite well as an Undead patron, from Strahd to Azalin to Lord Soth. So, it's very much a good choice for Ravenloft, but I think it works in basically any D&D setting quite well.

Let's get into it:

Undead Spells:

1st: Bane, Rack of Sickness

2nd: Blindness/Deafness, Phantasmal Force

3rd: Speak with Dead, Summon Undead

4th: Greater Invisibility, Phantasmal Killer

5th: Antilife Shell, Cloudkill

    Naturally, Warlocks need to use spells that scale well if they're natively 1st-to-4th level. Greater Invisibilty sadly doesn't upcast. Summon Undead is probably the go-to concentration spell for us (having used it a lot on my Wizard, the 5.5 update for it has made the Ghostly and Putrid options quite powerful, as long as foes aren't immune to fear or poison, respectively).

Level 3:

Form of Dread:

As a bonus action, you can beocme an avatar of your patron, gaining the following benefits for 1 minute or until you are incapacitated or end the form voluntarily. You can do this Cha times per long ret. The benefits are:

Facsimile of Life: You gain temp HP equal to 1d10 plus your Warlock level.

Fearless Form: You have immunity to the Frightened condition and end it if you are frightened when you activate the form.

Frightful Avatar: Once per turn, when you hit a creature with an attack, you can force them to make a Wisdom saving throw or be frightened until the end of your next turn.

    I think this is totally unchanged (maybe it was PB times per Long Rest in Van Richten's) but it's a solid option that should be available most combat unless you're in a real grueling dungeon-crawling campaign.

Level 6:

Grave Touched:

You get the following:

Arcane Necrosis causes Necrotic damage you deal to ignore resistance. Also, once per turn, if you cast a spell that deals damage, you can make that spell's damage Necrotic.

    Once again, I think this is unchanged. Given that Warlocks have Force as their main damage type, this on its own isn't going to often be much of a benefit. Also, I think very few monsters have resistance rather than full immunity to Necrotic.

Dreaded Necrosis allows you, when you hit with an attack that deals Necrotic damage while  you're using your Form of Dread, you can roll one additional damage die once per turn.

    As a reminder, the new Pact of the Blade allows your Pact Weapon to deal Necrotic, Psychic, or Radiant. So this should work for Bladelocks as well. This is the main reason to use Arcane Necrosis, even on a reliable spell like Eldritch Blast, unless you're fighting ghosts or something. Basically, turn one of those hits into a crit.

Undead Endurance prevents you from gaining exhaustion from dehydration, malnutrition, or suffocation, and you don't need to sleep and can't be magically put to sleep.

    So, no worries about food or drink, and you don't have to breathe. Depending on the campaign, this might not come up or it could be quite helpful. (Notably, I made a Reborn Undead Warlock for a very brief West Marches campaign, and so there's a little redundancy there).

Level 10:

Necrotic Husk:

You get the following:

Necrotic Resilience gives you resistance to Necrotic damage, and this becomes full immunity if you're in your Form of Dread.

Unholy Resuscitation allows you to cause an explosion of deathly energy if you drop to 0 HP. Each creature in a 30-foot emanation of your choice makes a Con save, taking 2d10+Cha necrotic damage on a failure or half on a success, and then your HP becomes twice your Warlock level and you gain 1 level of Exhaustion. You can use this once per short or long rest.

    Couple things: first off, you can use this far more frequently than before. The old version required you to finish 1d4 long rests, one of the rare features that didn't necessarily come back the next day. That's a buff. The potential very subtle nerf is that it doesn't say if you "would" go to 0 HP. Instead, it's if you do, then these things happen. Thus, technically, in a strict reading, you do momentarily go unconscious, which means that you'd drop concentration and Form of Dread if that happened.

    As a DM, I'd probably rule that this should work like other features that allow you to avoid going down, but it's a weird little wrinkle in there.

Level 14:

Superior Dread:

Your Form of Dread is improved in the following ways:

Dread Resistance gives you resistance to bludgeoning, piercing, and slashing damage.

Ghostly Flight gives you a fly speed equal to your speed (and you can hover). You can also move through creatures and objects as if they were difficult terrain, taking 1d10 force damage if you end your turn inside one (is that here in, like, all of these Horrors Within subclasses?)

Profane Casting lets you cast Conjuration and Necromancy Warlock spells without any spell components unless there are costly or consumed ones.

    This is the only really huge change to the old version, replacing Spirit Projection. The old feature required you to park your physical body somewhere out of the way while you spirit gained these benefits. This is more elegant, but not as funky. It also lasts shorter, as the old Spirit Projection lasted an hour.

    But, this is probably better, as you're probably using Form of Dread anyway, and the old version of this could only be used once per long rest.

Overall Thoughts:

Up until level 14, this feels very much like a slight tune-up and update rather than a significant redesign, and honestly, even Superior Dread is largely just refining the existing feature.

But that's fine, because Undead Warlocks were already a solid subclass. Given how Warlock subclasses have changed in 5.5, I'm happy to have a revision for this one - I'd honestly thought it would have been a good choice for the Player's Handbook.

Anyway, that brings us to the end of the Horrors Within subclass review. I'm going to look at some other things, like Species, Dark Gifts, and probably go over a few of the monsters as well.

Blaster Goo-Lock vs. Death Knight

 We've been looking primarily at weapon-based builds that mostly involve just attacking with weapons, which does make the math relatively simple, but here I wanted to go to my very first character concept and see how they compare.

There's a lot of discourse that talks about how spellcasters are just more powerful than non-spellcasters in D&D. And I think that's probably true in a general sense - my Wizard can just do so many more things than our party's Fighter/Rogue. One could imagine that martial characters would still excel in single-target damage, but some spells (primarily Conjure Minor Elementals, but others as well) can allow a caster to overtake a martial character even in that scenario.

Part of this, I think, is that people don't really play D&D the way that its design leans: essentially, people rest far too often compared to how often they get into fights. Martial characters often don't have to burn resources to be at near-top-form. If the Wizard is relying on cantrips most rounds, then yes, a Barbarian is probably going to do way more damage than they do. But I think when you only have a few combats per day, the casters never have to play all that conservatively. And I will say that this isn't entirely players' faults: I think that the output of damage that monsters do compared with the amount of HP that players have also means that players want to take a rest more frequently than the game's resource systems are designed around.

I did a post a while back determining how many encounters using the 2024 DMG's encounter-building system we should have using the 2014 DMG's "Adventuring Day" value's worth of XP. It's a bit unhinged - and given how conservative the 2014 encounter-building rules were, you'd have a massive number of fairly trivial encounters if you used it.

Notably, 2024's DMG got rid of the section on the Adventuring Day. While I think very few people actually used it, and I think that the designers reasoned that players these days treat combat more as action set-pieces than something you're going to deal with in every room of a dungeon, it does actually mean that there's a crucial piece missing in figuring out the overall difficulty of a day's adventure.

But of all the full spellcasting classes, I think the Warlock is somewhat bounded because of its weird, unique spellcasting system.

Warlocks will never have more than 4 spell slots, though to be fair, at higher levels they also get their Mystic Arcana. This encourages them to treat spells a little differently - especially in single-target situations, they're usually best off picking a good concentration spell and then using something unlimited, like Eldritch Blast or a Pact Weapon, to be their main action over the course of a fight.

Warlocks have fairly simple gameplay because of this limitation, but building them involves a lot of complexity through Eldritch Invocations.

We thus have a ton of ways to build out even a pure Warlock character, but I'm going to just go a single, simple route: We're going to make an Eldritch-Blast-focused Great Old One Warlock, and we're going to see how they do versus a Death Knight at level 10.

    Feats:

Ok, as usual, we're assuming we take a background that allows us to boost our Charisma, and via Point Buy or Standard Array, we'll start off with a 17 Charisma at level 1. I've been ignoring Savage Attacker for the martials here, and really just ignoring Origin Feats overall, so I shan't start incorporating them now!

At level 4, I'm tempted to deviate from my usual: War Caster is a fantastic feat, but the main benefit is that we get advantage on Concentration saves. That's super-valuable for a Warlock who doesn't have a lot of other spell-slots to re-up a concentration spell, but we can take Eldritch Mind instead as an Invocation. The other benefits of the feat - the spells-as-opportunity-attacks and ability to do somatic components with weapons or shields in hand are... not actually that useful for us. We're going to be staying way the hell away from our foes if we can (though we might need to dip in briefly to establish a clairvoyant connection) and this ain't a Blade pact build (though even then, a Pact weapon can be used as a spell focus).

So instead, I'm going to grab Spell Sniper. This will let us use Eldritch Blast in melee without any penalty, and then it will also let us ignore partial cover when we attack with it.

At level 8, we could just take an ASI to cap out our Charisma, but I think that's leaving some tasty tools on the table. Some of the usual hits are a bit less appealing - Fey Touched, for example, is a common choice because Misty Step is so awesome, but not when you have to use your very limited 5th level spell slots to cast it (after one free casting, of course). Telepathic is also a bit redundant with our Great Old One subclass features.

Telekinetic, on the other hand, is thematic and not terribly redundant, and we don't really need our bonus action very much (which we'll talk about in Spells) so we can use the Telekinetic Shove very frequently. I think this is probably the one to grab.

    Invocations:

At level 10, we'll have 7 Eldritch Invocations. Let's get the obvious ones out of the way:

Agonizing Blast is a must-have, helping our Eldritch Blast scale almost as well as a weapon (actually scaling just as well as a nonmagical weapon,) meaning we're doing about as well as a Fighter with a Heavy Crossbow or Pistol.

Eldritch Mind is then a must-have because we're skipping War Caster.

Now, what about a Pact Boon? We're skipping Pact of the Blade because that's not the build we're going for. Pact of the Chain could give us advantage on one of our attacks, which isn't nothing. Probably our best bet for this purpose, sadly, would be a mundane beast rather than any of our special options to get something with Flyby, though I do really like the Sphinx of Wonder's Burst of Ingenuity reaction. We'll set this aside for now.

Actually, if we're just getting a mundane familiar, we might as well get Pact of the Tome instead, with which we can get Find Familiar as our free ritual spell. I like this pact boon a lot, but I think our main cantrip is going to come with the class anyway, so again, we'll save it for if we have extra slots left.

Repelling Blast won't increase our damage, but it's a fantastic bit of utility (especially as we get more blasts leveling up).

Gift of the Protectors is, again, not going to boost our damage, but it can keep one of our friends up, so I think it's worth grabbing. This does require Pact of the Tome, so if we take it, that's 5 claimed, and two left.

Fiendish Vigor is ok, but it notably doesn't say you get False Life automatically prepared - you can just cast it without a spell slot, and get a flat 12 Temp Hp. That's actually pretty good for keeping you a little more resilient over an adventuring day, but it doesn't scale with your level at all.

Honestly, there's not a lot left to just boost damage, so I'd personally take Devil's Sight, Mask of Many Faces, and, let's say Lessons of the First Ones to grab something nice like Tough, Lucky, Alert, or what-have-you. This last one might be less valuable if we're already, like, a Human with two Origin feats. We'll assume we have Lucky somehow.

    Spells:

Our concentration and our spell slots are precious, so this will probably be pretty simple.

Our main "thing" is going to be Eldritch Blast, which resembles a Heavy Crossbow for a martial in a few ways: it does 1d10 damage, we add the 4 of our main ability modifier to damage, we push targets pack 10 feet when we hit them, and we get to make two attacks per turn.

In terms of non-concentration spells to consider, Armor of Agathys is good for both protection and to punish attackers, but ideally we're going to stay the hell away from our Death Knight adversary, and let the melee martial characters tank it. If we had the minute and components to cast it, Magic Circle could really work wonders at protecting us from the Death Knight. But we'll assume we can't really do that.

Thus, we're going to focus mainly on just a single concentration spell and our cantrip on subsequent turns.

I think there's an argument for Hunger of Hadar here - Death Knights have Darkvision, but that won't pierce the darkness of the spell, and because we have Devil's Sight, we'll be getting advantage on our attacks. Furthermore, if the Death Knight tries to move out of it, we can use our Repelling Blast and/or our Telepathic Shove to push them back into it. Both damage types from the spell will be effective against the Death Knight, but there's no save against the Cold damage, so we'd pour our upcasting into that, doing 4d6 cold at the start of the DK's turn and then 2d6 Acid on a failed save.

There are a couple problems, though: first is our friends. Hunger of Hadar is kind of area-denial, and sadly that applies to our party members as well. If we think we can reliably box the Death Knight into it (get a friend to cast Wall of Force around it, or something) it'll be great, but if we want some melee characters engaging with the Death Knight, this will hinder them.

Second, the Death Knight can move with legendary actions. So even if we push them back 20 feet, and even another 5 with our Telepathic feat, and they're in difficult terrain, they can still do 37.5 feet of movement each round, which will get them out of the spell's radius. (Granted, if you put it in a bottleneck, that might run them into your melee folks).

I think this would be a really cool play, but I think the simpler option is what I really wanted to build around anyway, which is Summon Aberration.

Now, for pure damage output, the Mind Flayer (formerly Star Spawn) option is going to do the most because of their Whispering Aura. But these spirits are pretty fragile - it'll only have 50 HP and an AC of 16. The safer option is to use the Beholderkin, which can hover and shoot rays at a range of 150 feet. Put them far away from any of the party so they don't get caught in a Hellfire Orb and you should be ok as long as you maintain concentration.

    Game Plan:

This is pretty simple: We cast Summon Aberration on turn 1 (it's an hour duration, so if we know things are about to pop off, we can cast it ahead of time, but I'm assuming the fight comes as a bit of a surprise).

Next, we scoot up to just within 30 feet of the Death Knight and attempt to use Clairvoyant Combatant on them. Full disclosure: if the Death Knight fails, they will probably burn a Legendary resistance, so this probably won't do anything. But it's worth a shot, if only to burn that LR.

Our familiar acts on its own initiative (barring a home rule) and so we'll have it Help whoever hits the hardest in our party. We'll have it take an Owl form so that it can fly, help, and then fly out without provoking an opportunity attack. Like the Beholderkin, we want it to spread out to avoid AoE spells. Because this might go to helping, say, the Paladin, I'm not going to include it in our calculations.

We have our Aberration fire two Eye Rays at the Death Knight.

On turn two, we will use Eldritch Blast to attack the Death Knight twice, and then have our Aberration keep shooting.

    Lucky and Advantage:

We'll have 4 luck points at this level. Lucky and Heroic Inspiration have kind of flipped in 5.5, so this will just grant advantage, or disadvantage if we're attacked. We could use this on two rounds of Eldritch Blasts to get advantage on all four of those attacks.

I... boy, here I think that the white-room optimizer nature of this series suggests that's what we should do, but in practice, I'd for sure hold this for, like, a saving throw against Hellfire Orb or Command or something.

Ok, bowing to the real world of actually playing this game, I'm going to say we're not burning Luck Points to get advantage on attacks. Sorry.

    Eldritch Blasts:

We have a +8 to hit here, meaning we have to get a 12 or higher on the die, and so we have a 45% hit chance. Without advantage, unless we're using our Familiar for it or Luck Points, that's just going to be it.

Our damage is 1d10+4 at this point, or about 9.5, with a 5.5 bonus on a crit. Thus, 9.5x45% is 4.275, and our crit bonus is 5.5x5%, or .275, so our total damage per attack is 4.55. Double that and we get 9.1.

    Aberration:

Our summoned Aberration is going to be doing a bit more: they have the same hit/crit chance, and it's also doing two attacks. Each hit lands for 1d8+8 at this level, or 12.5, and adds 4.5 on a crit. So, 12.5x45% is 5.625 and the crit bonus, 4.5x5%, is .225, giving us 5.85 per attack. Double that and we get 11.7.

    Summing It Up:

Thus, we get 20.8 damage per turn starting on turn 2.

That's actually well behind what we were getting on our other builds.

I will argue, though, that we bring some utility here, especially with Repelling Blast, which is a no-save pushback. With our long range on our attacks, we could spend potentially a couple rounds just pushing the Death Knight away from us if we can hit them from far enough away.

Let's try something different:

If we can bottleneck the Death Knight in a corridor or something, and we have a couple of meatshields - say a Paladin and a Barbarian) to block the way, let's see what we can do with Hunger of Hadar. Our melee allies would stand at the edge of the spell, unaffected but preventing the Death Knight from getting through. While they wouldn't be able to see the Death Knight inside it, the Death Knight is also blinded, and thus both our allies and the Death Knight would be making straight rolls. We, however, would be making attacks at advantage.

We give up our Aberration's damage, which is a big blow, because they actually hit harder than we do. But we gain the damage from Hunger of Hadar and also the increased damage because of our Advantage.

We're also assuming that the Death Knight will A: not burn legendary resistances against Hunger of Hadar and B: not retreat out the back of it. These are some generous assumptions, but it's what we're working with.

    Eldritch Blast:

The damage is the same, but we now have a different hit and crit chance. These will be 69.75% (wait, did I mess up the math in my Barbarian post? I think I had this as 67.75, but I calculated the miss chance as 55% squared, and found the difference with 1, and got this. Oh well, the Barbarian was winning anyway). And then, 9.75% chance to crit.

9.5x69.75% is 6.62625 and 9.75%x5.5 is .53625, so our total damage per blast is 7.1625. Double that for our two blasts and we get 14.325 per turn - after turn 1.

    Hunger of Hadar:

Cast at 5th level, we'll be able to add 2d6 to either (or one to each) the acid or cold damage of the spell. Because the Cold damage has no save, we'll do that. Thus, when the Death Knight starts their turn in the spell, they'll take 4d6 cold damage, and then at the end of their turn, they'll take 2d6 Acid damage if they fail a dex save at the end of their turn. Again, we're assuming we can keep the Death Knight in there the entire time.

So, 4d6 cold damage, no save, means 14 damage every round.

Then, there's the Dex save. This is a save-for-none, so it only works if they fail the save. Death Knight have Magic Resistance and a +6 to Dex saves. Our DC at this point is 16, so they fail on a 9 or lower, a 45% chance, but because of advantage, they need to fail on both dice, so it's 45% squared, or 20.25%. The damage is 2d6, or 7 on average, acid on a failure, so on average, that's 7 times 20.25%, or 1.4175.

Thus, the damage we're getting from Hunger of Hadar becomes 15.4175.

    Summing it Up:

This brings our total damage to 29.7425, which does beat our both our Rogue and our Artificer, but falls behind our Eldritch Knight and our Berserker, and this is in a scenario where things really favor us.

    One Last Thing:

Honestly, there's an alternative here: What if we just blow our spell slots on Synaptic Static?

Synaptic Static does 8d6 psychic damage, basically a Fireball that targets Intelligence and has some nice knock-on effects, but is also two spell levels higher. Death Knights only have a +1 to Intelligence saving throws, so they need to roll a 15 or higher, and still take half damage on a success.

Weirdly, we can kind of treat this like Graze in that way - the equivalent of 4d6 is hitting them no matter what, and they save to avoid the other 4d6 (is this actually easier? I don't know). So, they've got a 70% chance to fail on the save, though this becomes 49% because of advantage (70% squared). Thus, they have a guaranteed 14 (well, average) damage coming their way, and then a 49% chance to take another 14, which comes to 6.86, so the spell is doing 20.86 damage to them on average.

That is actually very, very slightly better than our Eldritch Blast/Aberration. However, we can only sustain it for two rounds, whereas the EB/SA version is sustainable for literally an hour, and our Hunger of Hadar version can last a full minute.

Death Knights actually don't have a ton of hit points - only 199 - for a creature of their power so if you're in a party with other big damage-dealers, doing the simplest and burstiest kind of damage might actually be the right call.

That being said: the truth is that D&D combat doesn't happen in a vacuum, and you can combo with other players in a lot of fun ways. The forced movement of Eldritch Blast can be very helpful, and blinding the Death Knight with Hunger of Hadar will, among other things, prevent them from using Command or Fell Word.

I'll also say that my choice of Death Knight as the target of these builds, along with the lack of any magic items (like a Rod of the Pact Keeper) does disadvantage builds focusing a lot on attack rolls, as DKs have pretty high AC for this level.

Again, I suspect that a Death Knight would be very likely to burn a legendary resistance on Clairvoyant Combatant, and they'd already have to roll quite low for it to work in the first place. There are tons of monsters for whom I think this build would be a lot more effective.

So take all those grains of salt.