This is the first in a series of posts taking a brief look at the main deviations in the McHack when compared to traditional BX rules.

I have wanted to reduce the number of Hit Points in D&D for a long time, especially the spiraling HPs of PCs at even medium levels. In traditional D&D, which I would argue is a high magic setting, the problem of higher character HP is mitigated by the rise in powerful magic at higher levels. In the low magic sword-and-sorcery setting of The McHack, high HPs are a real problem: combat becomes long. boring, and tedious. So I decided to lower HPs in a number of ways.

Lowering Hit Dice

First, I decided to make the default Hit Dice for PCs a D6, regardless of class. I felt that a D8 was too much of a swing from 1 to 8, and it also never made much sense to me that Fighter got a D8 for HP while a Mage got a D4, regardless of their relative Constitution scores? However, as a concession to the old way of doing things I gave non-martial classes just +1 HP at certain levels, instead of a whole new HD. I also lowered creature HD from a D8 to D6, so effectively fighters were not losing ground on their foes, non-martial classes had the potential to be a bit tougher, and the whole thing was a lot simpler everyone uses a D6.

Capping Hit Points

Next, I have always wanted to put a limit on HPs. It just seemed silly to me that a person could gain more Hit Points than a dragon! I think a large part of the challenge and fun of D&D comes from the danger, and the vulnerability of the characters. High HPs can make some characters feel invincible, and that is less interesting to me.

I also felt that Ability Scores in D&D were not particularly important. I understand that this has some benefits, but I wanted them to mean something. What if we used Constitution as the cap for HPs? That way CON is directly responsible for how much damage a character can take.

I liked this concept a lot, but I felt it set the cap a little too low (most PCs will have a CON of 11-12, maybe 13-14 at higher levels, and that didn’t seem like quite enough. So, I settled on the following formula – it’s not quite as clean as CON alone, but I think it brings us to the point where PCs get tougher but are still vulnerable:

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HP Cap = CON Ability Score + Current Level

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Minimizing CON Modifier

Lastly, I had to deal with the Constitution Modifier which, for characters with a good CON score adds 1, 2, 3: or even 4 to HP per level! Clearly this was not going to fly with the HP Cap. Most Ability Modifiers do not stack in the way CON adds more and more HP every level (the DEX Mod gets applied to AC once, the same is true for STR damage modifiers, WIS Magic Save Modifiers, etc.) I also realized that if we were already using CON as the basis for the HP Cap, to put too much weight on the CON Ability Modifiers would be to duplicate the effect of a high (or low) CON on HPs, so I decided to add the CON Mod only once.

The result is a spread of HP that (outliers not withstanding) gives most PCs 3-4 HP/LV. If we assume median CON scores of 11/12 with PCs opting to improve CON once every three levels that means most PCs will cap-out around LV4/5 and simply increase by 1 HP/LV thereafter. And in my game, most PCs don’t even get to LV4/5…