Converting my Fighter to the One D&D Playtest Version

 The longest-played character I have is my Eldritch Knight Fighter, Jax Sardare, a blue dragonborn who is level 12.

Jax is built to be very hard to hit. He has the Defensive fighting style, and wears a set of adamantine plate and a +1 shield. This puts his AC at 22, but when a creature rolls a 22-26 on their attack roll, if he has a reaction, Jax will cast the Shield spell. Thus, until he's out of spell slots, he has an effective AC of 27.

At the point in the campaign when things sort of fell apart, between one player whose individual story was central to that of the campaign having to step away given that he had become a father and did not have the free time he used to and our DM taking on a lot of new work that made her too busy, we had been on a sort of tangent where we were dumped into the Nine Hells through a cursed portal that had stripped us of all of our gear (we were all literally naked when we landed in Avernus). We managed to rebuild a small collection of gear, which for me meant some chain mail, a shield, and a +1 Mace.

So, this dropped my AC to only 19, but I still had all my class abilities. I had a non-magical Flail as well.

Let's look at how we'd convert Jax to the new D&D system.

First off, he gets a free feat. Jax already has the Tough feat, which he likely would have taken as his 1st level feat. His other feats have been spent on ability score improvements (maxing out Strength with his level 4 and level 8 feats, and bumping Con up from 12 to 14 at level 6. I had assumed that Intelligence was going to be more important than it wound up being for an Eldritch Knight, so had prioritized it over Con, starting with a 14 in it. Charisma was 12, Wisdom was 11, and Dex was 10). With the level 12 feat freed up, I suspect he would have taken War Caster at level 12, which I'd intended to do before I realize I wanted higher HP as a higher priority. Despite being an Intelligence caster, the 1-point bonus would have allowed me to bump my Wisdom score to 12 and thus get a +1, so I might have gone with that.

So, with these, we get a Strength of 20, Dex of 10, Con of 14, Int of 14, Wis of 12, and Cha of 12. (I might have also chosen to boost Intelligence or Constitution instead of Charisma if I had made the character after the Tasha's rules around racial ability score bonuses were introduced, but I'm going to leave those for now).

While I never got to play him as such, I had converted him to a "Chromatic Dragonborn" from Fizban's Treasury of Dragons. But if we want to fully move forward into the One D&D version of him, we can try the most recent version of the Dragonborn Species.

So, right off the bat, we lose the Lightning immunity that you can get from the Chromatic Dragonborn, but gain a couple things.

He can now use his Breath Weapon in place of one of his three attacks on a turn. This deals 3d10 Lightning damage on a failed save with a DC of 14. That gives us 16.5 average damage compared to the 14 from the old breath weapon (2014 version) and becomes just one attack among many. It's also usable four times a day, compared to typically 2 per day with a single short rest.

Jax would also now have Darkvision.

Finally, Jax would be able to gain a fly speed of 30 feet for ten minutes once per long rest as a bonus action.

    So far, Jax is almost strictly better, and only possibly better if we have four or more short rests per day.

Now, let's take a look at his capabilities via his class.

We don't yet have the updated version of the Eldritch Knight, which I presume will be reprinted in the 2024PHB, but with the new version of the Fighter, we can take a look at a few things.

Fighters, as I looked at with the post I made on Fighters, pretty much didn't lose anything with the changes made here. Indomitable is far more powerful than it was, and Jax would, by this level, have access to Weapon Mastery and Weapon Expert.

The one true loss, though, is that he can no longer use Action Surge to cast two leveled spells in a turn. Action Surge is now limited to a set number of actions (including attack) which means no double-Shatter. To be fair, I only did that I think once in the whole campaign, given that I was pretty conservative with spell slots to retain the chance to cast Shield, and mostly used my spellcasting feature for Green-Flame Blade and Booming Blade cantrips. Now, I also can't cast these twice with action surge, but typically I wouldn't anyway, as I think the math only made it worth casting these cantrips thanks to War Magic if I couldn't trigger their secondary damage - one cast would allow the bonus action attack, and then I'd want to just make three normal attacks using the Attack action.

So, at this point, we just need to look at how Weapon Mastery and Weapon Expert would apply to his situation.

He has a +1 Mace and a nonmagical Flail. Interestingly, both of these weapons have the Sap feature.

This actually plays into his identity as a tank, as he'd be able to impose disadvantage on attacks with his weapons. This should work even when hitting a creature with the attack that is part of Green-Flame Blade and Booming Blade.

With only two weapons on him, he's actually got three other masteries to spare. His previous weapon was a +1 Battleaxe, so he might have kept that mastery active in the vain hope he could get back to the Prime Material Plane and get his stuff back (even if that campaign is over, I'd love to do a quick one-shot where we at least get to not be in the Nine Hells anymore).

Now, what might I replace Sap with on these weapons? I'm likely to be using the Mace, given its magic property - 1d6+1 is the same average damage as 1d8, but especially in the outer planes, having a magic weapon to overcome resistances is very important (not to mention being able to hit more often).

Unfortunately, neither weapon actually qualifies for a lot of these masteries. In fact, the only alternative either of them get is Slow. I think Sap is usually going to be better than that in most cases, so I'm not really inclined to swap it out in either case. At the next level, I'd slap Slow on there as the second mastery - and swapping between these makes sense, as both are limited to one effect on a target per turn.

Let's imagine that I got my +1 Battleaxe back, though.

Natively, the battleaxe comes with Topple. That's actually pretty good, especially in a group with a Monk and a Paladin, who would enjoy the advantage bestowed with the prone condition. The DC here would be 17.

The Battleaxe is also eligible to get Flex, Push, and Slow.

Of these, I think Push is the one that appeals to me the most. Especially given that, as a Fighter, I can potentially hit three times a turn, if I followed after each hit, I could push a Large or smaller monster back a full 30 feet, which would got a long way to protecting the party's Ranger, Cleric, and Warlock/Wizard. It would also let me push the targets into harmful AoEs - the aforementioned Warlock/Wizard could drop a Hunger of Hadar and I could shove the monster right into it.

Flex I generally think is underwhelming in damage - it's only an average increase of 1 damage - so I think if anything I'd be more likely to trade that out for other properties when possible. Slow could be good, but I think Push is more versatile.

And, if you successfully Topple a target, that's usually going to be better at slowing them than Slow.

I will also say that, to me, the mental image of the Battlemage-like Eldritch Knight is all about creating shockwaves in the earth as they swing their mighty weapon. Both Push and Topple fit that fantasy to a T, and even if these are available to non-magic Fighters, I'd definitely flavor this as some arcane, magical technique.

So, if you read the last post about my ambivalence about the design of the ranged Warlock, this post has given me the opposite feeling. I am freaking excited for this version of the Fighter. I want to play this so, so badly (though let me get my old weapon back, please!)

For a sword-and-board style of combat, I think that Topple and Push are probably my favorite masteries to pick up. Now, Weapon Adept allows you to put two new properties on a weapon, not merely preserving the original in addition to a single added one.

Therefore, I'll be fine as long as my weapon has the Versatile property, which is the common property that makes them eligible for both Push and Topple. This makes Battleaxes, Longswords, Tridents, and Warhammers eligible to work for me, as well as Quarterstaffs and Spears if I'm willing to use a lower damage die in exchange for some great magic bonus.

Among these, the Trident is actually the stand-out. This now does the same damage as the other martial versatile weapons, but has the Thrown property on top of that (it also has Topple inherently). While I think Bludgeoning is usually slightly better than Piercing in terms of resistances, both are less often resisted than Slashing. And, as an Eldritch Knight, I'm particularly adept at throwing weapons, as I can call it back to me with a bonus action if I have it Weapon Bonded.

Yeah, I want to play this so very badly.

EDIT: So... this might be busted, but...

Push works if I hit with the weapon, regardless of if that's part of the attack action.

Booming Blade deals an extra 2d8 thunder damage up front, but then also 3d8 thunder damage if the target moves before my next turn. Now, sure, this punishment damage only works if they move willingly, but it means I can kind of bully the target - Booming Blade, blasting them for 3d8+6, then knocking them back 10 feet. Now, if they want to attack me, they need to walk toward me and take 3d8 more thunder damage.