Combat overhaul: damage scaling, injuries

I don't like looking things up in play. I also don't like asinine detail or unprincipled differences. The AD&D monster manual statblock is basically my worst nightmare.

You're telling me a wolverine is a 3 HD monster with claw/claw/bite? A wolverine can defeat three trained level 1 human combatants in armor? (They also have an extra +4 to hit, for a total of +7. Plate armor is meaningless to these beasts.)

I don't want to have to look up how much damage a creature does, and I don't want the answer to be some ridiculous bullshit. I want clear guidelines for monster damage, guidelines which I can apply consistently and on the fly, without consulting any books.

Principles

In my heartbreaker, I distinguish between HP (hero points) and IP (injury points). HP is protagonism, plot armor. Only people and monsters with levels have HP. (Nameless humans don't get HP.) You can lose HP all you want and still stay effective, as long as you've got at least 1 left. IP on the other hand is meat points. When you lose IP, you lose effectiveness (precise rules at the bottom) and when you run out, you die.

The average human has 3.5 IP, down to 1, up to 6. (Starting IP = 1d6, with a bonus or penalty die from Body.)

Benchmarks

So anything dealing 1d6 damage is lethal, though not an instant death. 1d6 damage = LD50. A successful sword attack? 1d6 damage. With modern healthcare, a fall from 40 feet? 1d6 damage. A pedestrian getting hit by a car going just on 80 km/h? 1d6 damage. A day without water? 1d6 damage. Almost any animal attack is going to be 1d6 or less, unless the animal is more lethal than a fucking sword.

Let's scale down a little. What does 1 damage? Whatever either kills the very weak (the weakest 5% or so of adults) or seriously injures an average person. You pass out after 2 minutes or so without air, so that's a good benchmark for 1 damage: you get 1 minute underwater free, and then 1 damage every 2 minutes after that, unless you have special training.

More low-damage examples.

• A bite from a black widow is a serious injury, but very rarely if ever fatal. 1 damage.
• A short uncontrolled fall. Twist an ankle or get a concussion, but almost certainly survive. 1 damage.
• A bite from a black widow. 1 damage.
  
• A bad flu. 1 damage.
• A bite from an Indian cobra, kills 20--30% of human victims. 2 damage.

These are all status-effect type things. But if you've got any HP left, you won't suffer the status effect. That kicks in when you run out of HP, and start taking IP instead. If you've got HP, and you have a short fall, you don't twist an ankle or get concussed, you bounce back up, good as new. If a black widow or an Indian cobra try to bite you, either you catch it just in time (total Conan move), or you're just so tough you don't give a shit, you just work through the pain. Maybe a high level fighter flexes so hard the venom gets ejected from the wound.

Now for some higher damage things. 1d6 is the most a normal human can reliably dish out with mundane medieval weapons. (Or most guns I'd say! At least judging by action movie standards.) So whatever does more damage (1d6+2, say) is probably super-normal. I'd give it some serious armor penetration to go along with the extra damage. So we're talking about things that rend through steel. I'm thinking troll claws and ogre clubs. Polar bears, crocodiles, and great white sharks probably live here too. Anything that can kill somebody around 60 or 70% of the time.

It's a fun feature of my combat system that, as somebody gains Attack Dice (which, in monsters and fighters, increase one-to-one with levels) they gain damage too; extra degrees of success on the attack roll each confer +1 extra damage on the target. So I think it's probably not necessary to explicitly give more damage to trolls, ogres, bears, and crocs; the attack rules already take care of their +2 damage! (Maybe further testing is needed here though. I might come back and revise.)

(A note on the formalism for larger damage sizes. We'll simply multiply all hits by 2 (or more). So a full hit will deal say 2d6 damage, an extra degree of success will deal +2 damage, a spite die will deal 2 damage. Mutatis mutandis.)

2d6 damage. That's a 90% fatality rate. Anything here is definitely going to have total penetration on mundane armor. When it kills you, you go "Crunch!". A T. Rex bite, a hug from an ent (which can tear stone), a smack from a steel golem. A shotgun blast to the face.

3d6 damage, 99% fatality rate. When it kills you, you go "Squish!" or even "Splat!". A bite from a dragon. A giant's club. (This actually is where AD&D puts stone giants! Yippee!) A siege engine.

6d6 damage, 100% fatality rate. When it kills you, you're dust. A weapon of mass destruction.

Really, when we get past 3d6, we should start benchmarking by comparing threats to heroes rather than ordinary people. But that will also require benchmarking fantasy heroes, which is difficult. So we'll simply leave this work undone for now.

Injury rules

Humans have Injury Points equal to their Body score divided by 3. Named humans, PCs, and monsters all have HP (hero points) as well. When you take damage, lower your HP. When you run out of HP, save or go into shock from the trauma, and start lowering your IP. When you run out of IP, you are dead.

When you lose an IP, you are always formally impaired; take a penalty die for every IP you're missing. You are also impaired in an organic way; whenever your injury suggests that a task would be particularly difficult, take an extra penalty die, walk slower than normal, require more food and water, whatever.

You recover IP at 1 per week of rest. (Contrast with HP; recover 1 HP/level after every fight, and all your HP after a night of rest.)

The actual injury represented by the lost IP takes however long to heal as it really would, if it will at all. So maybe at -3 IP you've lost a leg; 3 weeks later, you've got your IP back, but your leg is still gone, you'll have to learn to walk with a prosthetic, and you'll be taking penalties to movement speed, stealth, maneuverability, and so on for the rest of your life.

Feel free to soup up any injury description with a roll on a critical hit table. Maybe you'll get something fun, like a bleeding infected wound!

First aid treatment can treat diegetic aspects of injuries, and stop them from causing further formal injuries (for instance, if you have a 2 IP bleeding injury, and it goes untreated, you might take a further 1 IP injury, blood loss/anemia!), but won't recover IP without extraordinary skill. Low level healing magic is mostly used for diegetic effects and HP as well. It would take something really extraordinary, like a saint's Lay on Hands ability, to instantly recover IP.