El Dorado of Damage and Death

Great module title isn’t it?

Anyways. I’m generally against combat systems, but if you have to have them: the El Dorado of TTRPG combat and damage systems, to me, is one that’s as fast and simple as Into the Odd, but can be used to play D&D modules. I hate combat systems and HP and quantitative damage, but if I had El Dorado available, I’d probably use it to play B2 instead of the “FKR heresy” that’s usually my approach. Marcia B came up with a very nice candidate for El Dorado here – two, in fact. Marcia’s 2D6 goes: 2D6 under AC, and if it hits, highest die is damage. Marcia’s 1D20 goes: 1D20 under AC, and if it hits, it’s the damage. Very neat! Incredibly neat! Her calculations show it’s roughly in the same ballpark of deadliness (Ballpark of Deadliness – another module title) as OD&D and ItO.

Let’s run some numbers

Annoyingly we realized her proposals don’t scale well to higher AC and HP combat. For this, we calculated, for 100.000 simulated fights, the average number of attacks it takes for an attacker to deprive a defender of all its hit points, and the average damage over these rounds. See here (notice how predictably flat ItO is; also note the colors are on a log scale. And I apologize if this is hard to read on a cellphone):

The annoying thing to spot here is that both of her methods show extreme – multiple orders of magnitude – decrease of damage and increase of combat duration as you go from AC 8 to AC 2, and from 1 HP to 32 HP. So unless you kill off the party before they have the chance to reach level 5 and kill dragons, this probably will result in very boring dragon fights as they keep whiffing and whiffing and doing 2 damage every 36th turn.

Factoring in Attack Bonus

But wait, it gets more complicated! The above assumes the attacker has no attack bonus – it pitches 0th-level characters, or those without an attack bonus per level, against basically dragons and titans. So, let’s add character progression. How do these systems look like when the attacker does have an attack bonus? (I’m skipping Into the Odd and Avg. Damage this time because this is already a lot of data.)

So we see that both of Marcia’s systems mainly diverge from 0D&D at the extremes: when low-level characters are fighting high-HP monsters, they’re even more dead than in 0D&D. But when the situation is more evenly matched – say, an attacker with an attack bonus of 4 attacking a 4HD monster – the numbers are very similar to 0D&D! This may or may not be desirable or undesirable; on one hand it looks a bit like inviting “balancing and matching” of encounters to parties, which I think OSR people have great disdain for. On the other hand, doesn’t the OSR say that combat is war, not a sport, so dying in an outmatched unfair fight should be expected? Maybe this is good!

Here’s another way to visualise a slice of the same data.

This time, on the right, we’re pitching a character with a to hit bonus of 0 against an opponent with AC 6 and 2 HP, then bonus +1 vs. AC 5 and HP 4, all the way up to AC 2, HP 32 against a +4 bonus. Pretty close match between OD&D and Marcia’s methods! Of course, this is only for those classes who’re getting an attack bonus. On the left you got somebody with a static attack bonus of +0 going against increasingly stronger opponents. Notice the different y axes; on the left, you can see that an OD&D character without an attack bonus needs to attack an AC2 32HP opponent more than 1000 times on average in Marcia’s 2D6 system, on the right you can see that both in the 2D6 system and OD&D it takes around 25 rounds if the dragon killer brings a +4 attack bonus. I’m not sure, but it looks promising to me. Maybe we can reach El Dorado after all.

Credits

Thanks go obviously to Marcia, who came up with all this in the first place, and was very gracious when I asked her for help. Any remaining errors are mine. For example, she’d prefer to use her methods for a more narrow range of AC, but I wanted to see how it plays out over the range of Acs you might encounter in D&D.

You can find the (ugly, first-draft) code for these analyses in this pastebin.