Saturday, July 4, 2020

Complicating Armor Class in D&D

AC is a simple concept for D&D, at least in 5th Edition. The higher your AC, the higher someone needs to roll on an attack roll to hit the target. Players will generally hover between 10 and 20, depending on your character's build (my Eldritch Knight Fighter currently sits at 22).

For gameplay, it's pretty smooth and I think works well, but I also always felt like there was one big glaring weirdness with it:

Dodging an attack or deflecting it with armor are treated exactly the same way.

A Monk, for example, does not wear armor, and instead gets to add their Wisdom modifier on top of their Dexterity modifier. If you're diligent about stacking up both stats with your ASIs, you'll eventually get +5 to both and thus have 20 AC (which is the same as someone in full plate with a shield - in other words, quite good).

The notion of a Monk having high AC is that they are dodging very effectively - the Dexterity is their physical capability of moving out of the way when a sword or claw comes toward them, and the Wisdom represents their situational awareness - being able to anticipate where the blows will be coming from.

A Paladin, for example, once they amass a fairly large amount of gold, can get plate armor and, if it's their playstyle, they can use a shield to get their AC up to 20 (before accounting for magical items and such.) But the flavor of this is very different. As a big, metal-clad bruiser, the Paladin is relying not on getting out of the way of attacks, but instead for their tough armor to make attacks glance off of them.

Of course, this is all purely on the defensive side of things, too. When you make an attack roll, you're trying to aim your strike or shot or what have you at the target. If you roll low, you miss, but is that miss your fault, or just the fact that the enemy is too heavily-armored or agile and avoided the attack's consequences.

As a DM, I sometimes try to flavor misses in different ways.

For example, if a player attacks a highly dextrous but unarmored foe, we can break it down two ways: if the attack is below a ten, the player just failed the attack in some obvious way - you pulled the trigger on your crossbow too early and it went wide. This accounts for the free 10 points of armor class everyone gets before applying their stats. If it's above ten, but still misses, the target was just too adept at dodging and evaded the attack.

Then, when armor comes into play, things get a bit different. Basically, if the attack would still hit if it weren't for the target's armor - essentially if you subtract the armor bonus from the target's AC (leaving the dexterity, up to a max of two with medium armor) - you can say that the attack does actually hit, but is absorbed by the armor. So let's say you shoot at a ranger in Scale Mail - they're dexy, so they have 16 AC. If you get 1-9 on your roll, it's entirely your fault. If you get 10 or 11, they dodge out of the way, but if you get 12-16, that 4-point range is covered by the Scale Mail's 14-AC bonus, which means that, flavor-wise, the attack is deflected or caught by the scales.

Naturally, when it comes to heavy armor, there's no dodging at all - in this case, it's either a total miss below 10 or it's caught on the armor up to the target's AC.

You can even play this up with shields, where if the attack would have hit had the target not been using a shield, you can say that they deflect the attack with a quick block.

Now, you may ask:

What the hell is the reason for even thinking about this?

After all, the mechanics of the game don't care if you're dodging or deflecting attacks, and maybe your DM (or you, as a DM) simply say that the heavily-armored Death Knight is dodging out of the way of all the party's attacks.

That's totally your right to do so, but looking at things this way opens up new possibilities for homebrew rules.

Mind you, what I'm proposing would be a significant change to the rules and possibly break the game, but hear me out:

You could make a distinction between dodging and armor by making its interaction with damage work differently.

In real life, a shield doesn't magically negate an enemy's attack - it works in part by being a big heavy thing that absorbs the momentum of an enemy's strike and also in spreading the pressure of that strike to a wider surface. The reason we use blades, after all, is because they allow us to focus the force behind an attack on a relatively tiny surface area - the smaller the surface area, the greater the pressure. A bullet is a tiny object, and it's not all that heavy, but we launch them at such high velocities that they can pierce armor and bodies effectively - gunpowder weapons are part of the reason heavy metal armor isn't used anymore.

The idea behind a warhammer, then, is that you make it heavy enough that, even with a blunt surface, the force will be strong enough to crush the enemy. And that's before you even take into account that real warhammers tended to have spikes or relatively small heads - none of the kind of massive mallets that you tend to see in fantasy. They were more like a normal utility hammer on the end of a long pole.

So, I think you could separate Dex-based AC into something like "dodge chance." A Monk would be far more likely to dodge thanks to their Wisdom-based training, and would more or less be unchanged.

Armor, however, would work a bit more like the Heavy Armor Master feat - subtracting damage taken. However, HAM is kind of laughable as it stands now, only reducing damage by 3 (and only from nonmagical attacks.) When a young red dragon that hits you three times is going from 43 physical damage and 3ish fire to 34 and 3 ish fire, that's still roughly 80% of the normal damage you'd be taking - a hell of a lot less impressive than a Barbarian simply raging through that damage.

So I think, with this system, you'd want to make armor a lot more effective. For one thing, the expectation would be that you'd get hit a lot more, as, by wearing heavy armor, you're less likely to dodge attacks. (I haven't totally figured out how lighter armors would work, but if this system works it might not be too hard to hybridize it in a similar way to how it works now.)

For the sake of argument, let's start with the notion that your Armor (this is the new version, rather than AC) just reduces the damage you take (you could also make magic armor more important and hopefully easier to get by requiring magical armor to reduce magical damage) by an amount equal to its value.

So let's say that you're a newly-made paladin who fights with a two-hander, so you've only got chain mail, giving you 16 AC.

You've leveled up to the point where your DM isn't just being mean by sending you up against a CR 10 Young Red Dragon.

On average, in the current system, with the Dragon's +10 attack bonus for its bite and claws, it's going to hit you any time it rolls a 6 or higher, which is, conveniently for this example, 3/4 of the time. The bite hits for an average of 17 piercing and 3.5 fire damage, while the claws hit for an average of 13 damage.

So if we take the average damage and we multiply it by the chance the dragon has to hit you, we get the bite hitting you each round for an average of 15.375 and the claws hitting you on average for 9.75 (twice).

Add those up and we get 34.875 damage you'll be taking per round if the dragon focuses on you (and doesn't recharge their breath weapon).

Now, clearly, that's going to go way down if we just subtract Chain Mail's current armor value from the hits. While wearing heavy armor, your Dodge chance is just 10 - regardless of your Dex - and that means that with a +10 to hit, the dragon can only miss you entirely on a natural 1.

But what happens to the hits?

If it's purely subtractive, that makes the claws do nothing whatsoever even if they hit, unless the damage roll is high. Essentially, to do anything, the dragon needs to roll at least 11 on their 2d6, which means a 6 on one die and a 5 or 6 on the other - very unlikely. Meanwhile, the bite will do more damage - we can say the fire goes through regardless, and then the 2d10+6 means you'll need to get at least 11 on 2d10, which is actually the average roll for those dice, so about half the time that'll do damage to this fresh-out-the-box paladin.

So already, there's evidence that this system could have problems. The first thing I'd do is reduce "armor" by half or so. So Chain Mail now gives you 8 armor, which subtracts from attacks.

In this case, the Dragon still hits you 19/20 times. But when it does hit you, as long as it gets over 2 on its 2-die rolls, it'll wind up doing at least some damage to you. Basically, the average for the bite becomes the average of 2d10+6 (so 17) - 8 (so 9) plus 3.5 fire damage. The claws become the average of 2d6+6 (so 13) - 8 (so 5)... except that then I think I'm messing up the math because there are negative numbers skewing the average lower.

If we just ignore that issue for now to get a rough estimate, that means we're looking at a total of 9+3.5+5+5, or 22.5 average damage (well, times .95 because of the chance to get a natural one.)

That's still a lot lower than the current average damage, but feels more fair.

Here's the ultimate consequence of a system built like this:

It means a heavily-armored character will be far better at surviving hordes of small enemies that don't hit so hard. If you've got 30 skeletons stabbing them with shortswords, they'll barely take a scratch (in fact, unless they crit, a skeleton's shortsword damage maxes out at 8, so they will be entirely safe from them) while a comparably leveled Monk is going to, after 30 attacks, probably get hit a few times at least.

However, against a giant foe like, well, a giant, that heavy armor isn't going to be as effective, as subtracting 8 from a Frost Giant's Greataxe (average damage 25) is going to look less attractive than just out-and-out avoiding the attack about half the time (which a Monk with AC 19 would do.)

The question, then, is what you think of that consequence.

For my purposes, I'll happily stick with 5E's AC/+to Hit system, as it's very simply to understand and lets combat run smoothly.

However, this futzed-with system is, I'd argue, more realistic, and also introduces some interesting strategic possibilities for a D&D-like RPG system. (I'm well aware I might just be reinventing the wheel here, as I'm just not very familiar with non-5E systems.)

It would allow your heavily-armored fighter or paladin (or cleric, even) to wade through hordes of undead to rescue a beloved NPC with little fear, but when you want someone to draw the attention of a massive dragon, you'll probably want your agile Monk or Rogue to draw their fire.

I might have some homebrew to work on.

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