I must create a system, or be enslaved by another man's. I will not reason and compare: my business is to create.

- William Blake

Friday, December 06, 2019

The 10% HP rule (just a flesh wound)

It goes like this:

If an attack causes less than 10% of your HP in damage, it has no further detrimental effect on you (besides damage). No concentration checks, no death saving throws, etc. If damage stops spells in your game, damage that is lesser than 10% doesn't, and so on.

Something like massive damage in reverse, I guess (I dislike this rule in 3e, but 5e has an interesting variant in the DMG... that I find a bit unecessary).

The inspiration for my (probably unnecessary too) rule comes from an old game of Marvel Superheroes RPG (FASERIP).

If I remember correctly, I was playing as the Hulk... and, after taking massive damage from some super-villain, my PC got stabbed by a mook... and died!

I really hated that.

To be fair, I have no idea if this was because of the rules, of the game master, or just faulty memory (it was more than 25 years ago).

And, now that I think of it, it reminds me of Achilles... So, it might make sense in some contexts.

In 5e, it works as an anti-mook rule. This means your 15th-level fighter will not be executed by a kobold with a knife in a few seconds, just after being knocked out by a dragon. Also, the same kobold will not break your 15th-level wizard's concentration.

Again, this kind of grittiness has its uses, but doesn't quite fit the heroic fantasy tone of most official D&D stuff. Remember that the 15th-level fighter will probably survive a fall from any height!

In fact, if you want to make 5e less "bounded" and more "epic", i.e., the 15th-level fighter simply cannot be hurt by a single kobold, you might just ignore damage smaller than 10% altogether.

I have also considered a 50% HP rule as a complement... Say, if you WOULD take more than 100% of your HP in damage, the excess damage applies regardless of immunity.

So, in theory, the Tarrasque CAN hurt a werewolf with a bite, although it isn't easy.

AD&D had something like that IIRC. If you had enough HD, your attacks bypassed the usual "magic weapons" defense.

OTOH, some small creatures could be immune to fire, and swim in magma... So maybe this rule would only work for attacks?

I dunno. Maybe it is a case of rulings, not rules ("of course the Tarrasque killed the werewolf!"), or a matter of taste.


  1. Would a good balance point be to round base this instead of single attacks? I think of a high level fighter playing the Caesar to the kobold's senators would eventually start taking damage. This means that your single attacks still work, but mob attacks always hold weight.

    Your situational magma swimming really is a creature attribute that reduces damage in general, so I don't think it inherently needs to be treated separately.

    1. Yeah, doing a "damage resistance per round" would be a decent compromise.
      In the "magma" part, what I mean is that I want the tarrasque to hurt werewolves (immune to slashing damage), but do not want a magma mephit (immune to fire damage) to burn ion lava;.

    2. I guess you could reframe werewolf immunity to slashing damage as instead a higher DR threshold (for the lack of a better term for this 10% HP rule). Perhaps for slashing (or non sliver damage) the have DR 50%, so they reduce the damage by 50% of their HP, while silver cuts right through all that.

      So a heavy hitter with a sharp axe can still cut through a werewolf's DR, but not as effectively as if it were silver or magic.

      The lava mephit just isn't bothered by fire at all, so no damage is taken.

      Thoughts on implementing this idea, I would probably fold this into the class structure and possibly replace the Hit Dice System with a more static recharge rate. Perhaps you get Con mod tokens (minimum 1) to heal your DR in HP on a short or long rest. You hit 0 HP, you take CON damage (basically 1 maybe two hits) then I would say you are dead at 0 no save. If you don't die from CON saves, you heal 1 point of CON per period of time. This means that you are treated as a lower CON score to try and recover HP.

      Kinda rambling here. In short, I am thinking with this rule you would have to get rid of the Hit Dice mechanic to avoid to much on the HP side of combat.

  2. Theoretically good but it seems a little too crunchy to me in my old age

    1. I think you could streamline it with calculating the 10% value when your permanent HP changes.

      I would also specify with this that damage and poisons are two different metrics so that you can still have the risk of poisoned daggers even if the dagger "does no damage"

    2. In practice, I guess it would probably be too much crunch for me too. UNLESS, like Sean suggested, you could calculate this "damage threshold" beforehand and maybe use it for other things as well (e.g., HP recovered per day).

  3. I like the Crypts & Things rule that HP are dodging and when they run out of HP you take damage to your CON. CON is flesh and blood.

    1. I have a similar rule in Dark Fantasy Basic. However, I hadn't considering combining it with this one... might be a good idea.

    2. I think you just sold a book.