Hit points (HP) represent a creature’s capacity to sustain damage. Every creature has one more innate hit dice (HD) of a certain size, which are rolled to determine the creature’s HP. The size of the dice increases with the mass of the creature; eventually each hit die may even represent multiple actual dice.
In addition, hit dice can also be gained through leveling up. A first level human has one hit die as a human, with size determined by mass, and one hit die from first level, with size determined by character class.
The hit die for first level is maximized. In addition, for hit dice from level (but not from mass), the character’s Consitution bonus or penalty is added.
Hit dice for class levels beyond first are rolled, not automatically maximized; however, the die result cannot be a natural 1. The die is rerolled until the die does not show a 1.
The minimum number of HP from a single hit die is always 1, even if there is some penalty to its result.
Zero and Negative Hit Points
Being at zero hit points is not treated specially. However, going into negative HP means consequences. These differ depending on whether a creature is leveled or unleveled.
Whether combat-trained or not, creatures which are unleveled die at -4 HP. This means that at -1, -2 and -3, the creature is still alive, though in increasing levels of distress. During combat, at -1 hit points, a creature will be panicked and will turn berserk if that is a part of their nature (bears, boars, etc.) As well, at -1 hit points, the creature’s ability scores will be treated as 70% of normal. Most importantly, a creature’s action points (AP) are also lowered to the same percentage!
For example, if a creature had a Wisdom of 4 normally, at -1 HP the creature’s Wisdom would be rated at 2.8. If it had 5 AP normally, it would only have 3 (70% of 5 is 3.5, but we only count full AP.)
At -2 hit points, ability scores and AP are reduced further, to 40% of normal. Being this close to death will challenge the creature’s consciousness, so that a Wisdom check must be made based on its present Wisdom. The example creature above would have a Wisdom of 1.6, and only 2 AP. Furthermore, it would need to roll a 1 on a d20 to remain conscious.
At -3 hit points, ability statistics are reduced still further, to 10% of normal. As before, creatures must make a Wisdom check if reduced to -3 hit points. Therefore, unless the creature has 10 or more Wisdom normally, a Wisdom check at -3 hit points will automatically fail and the creature will fall unconscious.
Note that if a creature has been reduced to -2 hit points, and makes its Wisdom check and is subsequently reduced to -3, another Wisdom check must be made.
Creatures with at least one class level will not be killed unless reduced to -10 HP. Reducing such a creature to negative HP means a 10% reduction in the creature’s ability scores and AP per point below zero (e.g. scores and AP are 90% of normal at -1, 80% of normal at -2, etc.) Furthermore, a leveled creature does not have to check Wisdom against falling unconscious until they have reached -4 or lower HP. Similarly to unleveld creatures, a leveled creature reduced to -4 or less HP which makes its Wisdom check, must make another check to stay conscious if they are damaged again. Once they are unconscious, if they are healed above -4 hit points, they can make another Wisdom check to try and regain consciousness. Should they be healed to 0 or more HP, they regain consciousness automatically.
Note that class abilities will be affected if a character’s ability scores drop below the minimum for that class. Many spellcasting classes have minimum scores to cast certain levels of spells, but in addition, the following problems arise for a character whose ability scores have dropped below the class minimum:
- Talents and information from knowledge skills cannot be used or recalled.
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Bonus XP from high ability scores is not affected, since this would require the DM to track two separate types of XP: those earned when a character’s scores are above the cutoff for bonus XP (which is most of the time), and those earned when the scores have dropped (which is unusual but not that rare.)
Example of Negative HP Rules
For example, Albert, who possesses an 18 Wisdom, currently has 1 HP. He is struck for 8 damage and lowered to -7 hit points. This lowers his AP and his ability scores to 30% of normal, and furthermore forces a Wisdom check to stay conscious against his reduced Wisdom of 18 * 0.3 = 5.4. He rolls a 6 on the check, so he falls unconscious.
Just after Albert passes out, Bala casts Cure Light Wounds and touches Albert, restoring five of his lost hit points, bringing him to -2 hit points. Because his status has been altered, Albert makes another Wisdom check. With his current Wisdom of 14.4, he needs a 14 or less to succeed, but unfortunately he rolls a 16 and remains unconscious. His other friend Pyotr retrieves a healing salve and feeds it to Albert. Thankfully this gives him 2 more hit points, bringing his total to zero. Once Albert is at zero hit points, he automatically awakens without needing to make a Wisdom check.
(Rules and example altered from those by Alexis Smolensk.)