Being various and sundry interpretations of hit points & death.
By dying in the following examples I mean losing one HP per round.
Rules that allow dying characters generally provide some way to stabilize the dying character, either by performing an action or using a skill. Healing magic will also generally stabilize a dying character.
- Classic. Dead at 0 HP. Monsters and PCs are treated the same. Anyone can be knocked unconscious by bringing them to 0 HP with nonlethal damage. See below for the exact OD&D wording, which, as usual, is open-ended and ambiguous.
- AD&D. Dead at -10 HP. Unconscious at 0 HP and dying (DMG page 82). Monsters are dead at 0 HP and so are treated differently than PCs. 2E defaults to dead at 0 HP but provides an optional rule (which everyone I knew used) Hovering on Death’s Door (2E DMG page 75) which was basically the same as the original AD&D rules. [2012 06 16 edit: 1E AD&D is actually a bit more complicated; if you go from above 0 to -4, for example, death is immediate. See this comment for more discussion.]
- 3E. Disabled at 0. Unconscious and dying below 0. Dead at -10. Instant death if 50 or more damage is taken at once and a DC 15 fortitude save is failed (source: D20 SRD on death). Dead if constitution is reduced to 0 through drain or by taking constitution damage (source: D20 SRD on ability damage). Pathfinder is similar, but characters are dead at negative HP equal to their constitution score rather than at -10 HP (Pathfinder Core page 189).
- 4E. Dead at negative ½ max HP or 3 failed death saves. Incapacitated at 0 HP. A death save is required every round if a PC has 0 or fewer HP. Note saving throws in Fourth Edition are unrelated to either level or ability scores: there is always a 55% chance of success. Monsters are dead at 0 HP. 4E PHB page 295.
- Castles & Crusades. Unconscious at 0. Harder to heal between -1 and -6, but not dying. Dying at -7 to -9. Dead at -10. Feels like AD&D, but more fiddly. C&C PHB page 134.
- Lamentations of the Flame Princess Weird Fantasy Role-Playing (free downloadable Rules & Magic book, page 35):
When a character (or creature) suffers damage, the amount of damage is deducted from the character’s current hit points. When hit points reach 0, the character becomes unable to take any action, and in most cases falls completely unconscious. The character becomes mortally wounded at -3 hit points and will die in d10 minutes. No healing, magical or otherwise, can prevent death at this point. Death is instantaneous at -4hp.
This is surprisingly fiddly; before double-checking the text, I assumed LotFP was just dead at 0.
- Crypts & Things. When HP is gone, characters start taking constitution damage. Any constitution damage requires a save or the character falls unconscious. I don’t have a copy of this, so I am relying on the review over at Tenkar’s Tavern.
- ACKS. 0 HP requires a roll on the wounds table which may lead to anything from unconsciousness to injury or death (ACKS page 104). There are many potential modifiers to this roll, so the system looks somewhat fiddly, though I haven’t seen it used in play.
- DCC RPG. Dying at negative HP, dead at negative HP equal to character level (corollary: 0 level characters are dead at 0 HP). Any character that falls to negative HP but survives loses a point of stamina permanently. DCC RPG Open Beta Page 78.
- Robert Fisher: Classic D&D injury table. When a PC is brought to 0 HP, they must roll on the 2d6 injury table. Results include no effect, severed limbs, and instant death. Most monsters are dead at 0 HP, but important NPCs might get to roll on the table. See also Trollsmyth’s variant.
- Ramblings of a Great Khan: Save or die at 0 HP. When a character is reduced to zero HP, they may make a saving throw versus death ray (or whatever category is closest in the game you are playing). On failure, the character is slain. On success, they live but are knocked unconscious. There is a similar idea in this comment: the save is done after combat rather than immediately.
- Jeff’s Gameblog: One Last Breath:
Any time a PC runs out of hit points that character is allowed a saving throw versus Death if they haven’t already failed a saving throw to get 0hp. If the roll is made the character is at 1 hit point. At the Labyrinth Lord’s discretion they may also be stunned, unconscious, comatose, feverish, nauseous, mangled, bleeding, or otherwise in a world of hurt. If the saving roll fails, see the rules for replacement PCs below.
- Silver Blade Adventures: Wounded at 0 HP:
A house rule used in the World of Silver Blade is that characters brought to zero hit points or below are wounded and out of the fight, suffering ongoing penalties until the injury is healed, regardless of hit point recovery.
This is similar to Robert Fisher’s injury table, but a wound at 0 HP is assured.
[HP is] the number of points of damage the character could sustain before death. Whether sustaining accumulative hits will otherwise affect a character is left to the discretion of the referee.
Other relevant reading: