- Get shot repeatedly at point-blank range and shrug it off.
- Jump off a cliff, land face first, and walk away just fine.
- Survive getting stabbed by a lower-level character, and proceed to beat the crap out of them through sheer attrition and superior hit-points.
- Get set on fire and walk to the nearest pond at a leisurely pace in order to put it out.
- ...and other silly things.
To fix this, I use the following method in my games. Normally, I use LotFP for medieval-style fantasy, which these rules are adapted for. They're also, as it happens, roughly the rules used in Wolf-packs & Winter Snow.
Flesh and Grit points
Hit-points are divided into two distinct types. You have flesh points, which are actual physical toughness and resistance to injury. Losing flesh points represents being seriously wounded. You get cracked ribs, broken limbs, gaping wounds and blood everywhere. It's nasty as hell.
Grit points, meanwhile, are what people mean when they talk about how hit-points represent things like 'endurance' and 'luck'. Losing grit points explicitly doesn't represent being physically injured. Sure, you might be bruised or scratched, and you're losing stamina from the battering your taking, but you aren't actually taking any crippling wounds yet. Grit is, ultimately, an abstraction.
Normally, damage hits your grit first, and when all your grit is gone, the remainder rolls over onto flesh. Losing all your grit has no serious repercussions (other than making you vulnerable to real injuries), but without grit you're probably totally knackered and exhausted, covered in sweat and grime, with battered armour and torn clothes.
Maybe you're unable to defend properly against an attack. Perhaps you're shot by a concealed sniper, unexpectedly stabbed in the gut in mid-conversation, or caught prone in a brawl. Perhaps you've picked up a red-hot chunk of metal without protective gloves. Perhaps you've fallen in acid, or been knocked off a cliff. Point is, you can't back away, parry frantically, catch the blow somewhere that doesn't matter or otherwise try to fend it off. In this case, the damage ignores any buffer of grit you have left. Instead, it goes straight to your flesh.
In some cases, the protective gear you have will protect you from taking damage straight to flesh in this way. If you've got heavy gloves on, the damage from picking up red hot metal is buffered by your grit like normal. If you've got thick protective boots on, you can wade through acid and take it to your grit. If a mystery assailant bonks you on the head with a club, but you're wearing a sturdy helmet, grit represents your helmet's protection.
How much Flesh and Grit do you have?
For player-characters, your first hid dice (including any bonus points from constitution) are of flesh.
When you level up, your second hit dice (including any bonus points from constitution) are of grit. On top of this, every time you level up, you get an extra point of flesh, until you have the maximum possible result for your hit dice; that is to say the maximum possible roll plus your constitution bonus.
For monsters, it's up to the GM to eyeball it for each monster. Human-sized monsters probably only have one dice of flesh, and the rest as grit. Larger or particularly fearsome monsters like ogres and wargs might have two dice of flesh and the rest of grit. For particularly huge monsters like dragons, you can expect half of their dice (round down) to be flesh dice.
Monsters that need to be physically hacked to pieces and lack any real anatomy, such as oozes and zombies, have all their hit dice as flesh dice. Monsters that are supernaturally tough and lack real biology but still feel pain, perhaps vampires and demons, might have only one or two dice of grit and the rest as flesh.
Running out of Flesh; the simple version
So, what happens when you run out of flesh points? There's a two different versions of the rules here.
The simple version (which Wolfpacks uses) is that you're just dead. No more flesh, no more life. Do not pass go, do not collect two-hundred quid. You can also use this version for unimportant monsters and NPCs even when using the other ruleset, which speeds things up some.
The Complex version, or, How Flame Princess Got That Way
The more complex version works like this. When damage reduces you to 0 flesh or less, or you take any damage when you already had no flesh, look at the exact amount of damage dealt and get a result from the list below. It doesn't matter how far 'into the negatives' you are, just look at the result of the dice. Except for the penalties from actual injuries, you can keep on going just fine on 0 flesh; adrenaline can do impressive things.
One damage fucks your eye up. Maybe sight can sort of be restored by a skilled surgeon, with a successful medicine roll. This will take a day of treatment and require a month's time to heal before the eye's good to open. Otherwise, it's eye-patch time.
Two damage ruins a leg. With one leg, you're reduced to hopping about or relying on crutches. If both go, you're on the floor unable to get about at all. Roll a d6 for it. 1=left leg broken, 2= left leg mangled and useless, 3=left leg severed, 4=right leg broken, 5=right leg mangled and useless, 6=right leg severed. You might be able to fix this with a successful medicine roll. A broken leg will take a turn's worth of first-aid to treat, and need a week to heal up. A mangled leg will take a day's worth of surgery to treat, and need a month to heal up. If the roll to treat the injury fails, the best you can hope for is a peg leg. If your leg's chopped right off, well, you're fucked.
Three damage ruins an arm. Roll a d6 for it. 1=left arm broken, 2= left arm mangled and useless, 3=left arm severed, 4=right arm broken, 5=right arm mangled and useless, 6=right arm severed. A broken or mangled arm can be fixed with a successful Medicine roll. A broken arm will take a turn's worth of first-aid to treat, and need a week to heal up. A mangled arm will take a day's worth of surgery to treat, and need a month to heal up. If the roll to treat the injury fails, all you can hope for is a hook. If your arm's chopped right off, well, you're also fucked.
Four damage sets you bleeding. Each round, you lose a load of blood. You can bleed for a round for each hit dice you've got, and your constitution bonus (not a penalty, though) adds to this. A successful medicine roll to stem the bleeding means you're losing blood at a rate of of turns, not rounds, and a second medicine roll to stitch you up properly stops the bleeding completely. Any magical healing also fixes you completely.
Five damage knocks you out cold. You're unconcious for d12 turns, and you're bleeding out like above.
Six damage means you're gonna die. Bullet through the lung, horrible brain damage, innards ripped out, whatever. You get one more round to act in, and then you're dead. No medicine or healing magic will save you.
Seven or eight damage means you're dead instantly. Head chopped off, bullet to the brain stem or what have you. No last words, just gone.
Nine or ten damage means you're dead instantly, in a particularly nasty way. Maybe you've been chopped right in half through the ribs or had your guts exploded violently out.
Eleven or more damage turns you into something resembling salsa dip. Not only are you dead instantly, there's not even enough of you left to bury, resurrect or zombify. By and large, this calls for a polite round of applause from everybody who witnessed a death this impressive.
On top of this, certain really nasty attacks ignore flesh AND grit. Stuff like getting chewed up and swallowed by a dragon, or maybe a clockwork bomb grafted into your flesh just went off. You don't get to defend yourself with grit, and your flesh can't soak up any of the damage either. Even if you still have flesh left, look up how much damage got dealt, and get that injury. This is really, really rare however, and represents situations which would basically be instant-death in other systems.
All your grit comes back when you have a proper rest. Standing guard whilst the party thief fiddles with a locked door doesn't count, but the party stopping to cook and eat dinner absolutely does. You also get your grit back when you sleep. If you're particularly ill, weighed down by unreasonable burdens or whatever, you don't get grit back, however. You also don't get grit back if you've got no flesh left, assuming you're using the complicated rules for dying.
You get one point of flesh back when you sleep for the night. If you had a hot meal of proper food before you slept, you get an extra point of flesh back by sleeping. If you're sleeping in a warm, comfortable bed, you also get an extra point of flesh back by sleeping.
If you've got no flesh left, you only recover a single point of flesh by sleeping. If your sleep is disturbed, such as by a shift taking watch or bad dreams, you likewise only recover a single point of flesh.
When I run, I include Medicine as an extra skill. Like other skills, it has a base 1-in-6 chance to succeed, and like Languages you modify that chance by your Intelligence modifier. Specialists can put points in Medicine like normal.
You can roll medicine once to treat a fucked-up eye, arm or leg. If you fail the roll, then the body-part is ruined for good, save for magical healing. Injuries like having a tongue ripped out and so on might also be treated in this way.
You can roll medicine to stop characters bleeding. You can try this as often as you like, but it uses up a round's actions so you can't cast spells or fight when you do it. The first successful roll means the patient bleeds out in turns instead of rounds, and the second stops them bleeding completely.
Finally, you can use medicine to heal up lost flesh. If you succeed on the roll, look at the actual number shown on the dice. The patient gets that many flesh points back. If you fail on the roll, however, they take an additional point of damage if they had 2 or more flesh remaining. If they had only one point of flesh, or no flesh at all, roll a d6 and look at the results for How Flame Princess Got That Way to see what malpractice you just did.
Since you may be wondering, this is basically the same system Last Gasp Grimoire has, but altered some to suit my own tastes.