In a standard Pathfinder game, when a dragon with 800 hit points has taken 798 points of damage, it's still fighting at full capacity, but as soon as it has taken 801 points of damage, it's knocked completely unconscious. Though this ensures that injured characters remain useful and effective, it can feel unrealistic, and it devalues any healing that doesn't strictly prevent a knockout. Consider using the following variant to add tension and increase the strategic value of healing, but be aware that it can lead to situations that punish the side that's already behind, and that the pace of fights could drag in the late stages as two injured parties slug it out. Wound thresholds also make it especially dangerous for a party to take on higher-CR opponents.
In the wound thresholds variant, a character divides her hit point total into four quarters, and takes penalties whenever she's not in her top quarter. A character at 3/4 of her maximum hit points is less effective than one at full hit points, one at 1/2 is less effective than one at 3/4, and so on.
To prevent the need to divide on the fly, start out by calculating 3/4, 1/2, and 1/4 of your total hit points and add them to your character sheet as "Grazed (–1)," "Wounded (–2)," and "Critical (–3)." If you have a Constitution bonus of +1 or higher, also write down the negative of your Constitution bonus next to the word "Disabled." These terms indicate the conditions a character gains as her hit points drop. For example, a 7th-level sorcerer with a maximum of 71 hit points would become grazed at 53 hit points, wounded at 35 hit points, and critical at 17 hit points. If she had a Constitution score of 12, she would be disabled if she had 0 or –1 hit points, and would start dying at –2 hit points. As usual, she would die when her hit points drop to –12 or lower.
This rules variant uses three special conditions that apply automatically when a character reaches the corresponding wound thresholds: grazed, wounded, and critical. These conditions are not cumulative—only the most severe one applies at a given time. The disabled and staggered conditions have the same effects as in the core rules, but apply to a wider range of hit point totals, as described below. Unlike grazed, wounded, and critical, the disabled and staggered conditions stack, so a character who is disabled or staggered is still critical as well.
A character above her grazed threshold (3/4 of her maximum hit points) is healthy, applying no special modifiers. The character doesn't gain a condition in this state.
A character above her wounded threshold (1/2 of her maximum hit points) but at or below 3/4 of her maximum hit points is grazed. She takes a –1 penalty on all attack rolls, saving throws, skill checks, and ability checks, as well as to AC and caster level.
A character above her critical threshold (1/4 of her maximum hit points) but at or below 1/2 of her maximum hit points is wounded. She takes a –2 penalty on all attack rolls, saving throws, skill checks, and ability checks, as well as to AC and caster level.
A character at or below 1/4 of her maximum hit points is in critical condition. She takes a –3 penalty on all attack rolls, saving throws, skill checks, and ability checks, as well as to AC and caster level.
A character with a Constitution score of 12 or higher who is at or below 0 hit points is disabled until she falls below a number of hit points equal to the negative of her Constitution modifier. For example, a character with a Constitution score of 18 would be disabled from 0 to –4 hit points and unconscious at –5 hit points. A character with a Constitution score of 11 or lower is disabled only while she has exactly 0 hit points.
Instead of being staggered only when their amount of nonlethal damage equals their remaining hit points, characters using this system continue to be staggered from that point until their nonlethal damage exceeds their current hit points by an amount greater than their Constitution bonus, at which point they fall unconscious. A character with a Constitution score of 11 or lower is staggered only when her nonlethal damage exactly equals her current hit point total.
The penalty to caster level from the grazed, wounded, or critical condition can make it so an injured spellcaster is unable to cast the highest levels of spells she would normally be able to. However, it doesn't cause her to lose any prepared spells or spell slots. The penalty to caster level also reduces her bonus on concentration checks and lowers the range, duration, and effectiveness of her spells. The penalty can't make her effective caster level lower than 1.
Keeping track of wound thresholds for a horde of monsters can be a significant amount of work. To simplify the process, the GM can use only the wounded threshold and ignore the increased range for the disabled condition. This means she only needs to keep track of 1/2 of each monster's hit points and the –2 penalty. The GM should use this method primarily for large groups of monsters; prominent NPCs and enemies that fight on their own should use all the thresholds.
The following feats are either new feats or Core Rulebook feats adapted to work with the wound threshold system. Though the system doesn't require their use, they're a great way to expand the role of wound thresholds in your game.
Your healing is more effective if your patient is badly injured.
Benefit: When you cast a conjuration (healing) spell, it cures 1 additional hit point if the recipient of the healing is grazed, wounded, or critical. The additional healing increases by an additional 1 point at caster level 6th, and every 6 caster levels thereafter.
Harsh conditions or long exertions do not easily tire you.
Benefit: You reduce the penalty from being grazed, wounded, or critical by 1 (to –0, –1, and –2, respectively).
In addition, you gain a +4 bonus on the following checks and saves: Swim checks to resist nonlethal damage from exhaustion, Constitution checks to continue running, Constitution checks to avoid nonlethal damage from a forced march, Constitution checks to hold your breath, Constitution checks to avoid nonlethal damage from starvation or thirst, Fortitude saves to avoid nonlethal damage from hot or cold environments, and Fortitude saves to resist damage from suffocation.
You can sleep in light or medium armor without becoming fatigued.
Normal: A character without this feat who sleeps in medium or heavier armor is fatigued the next day.
You're especially dangerous against enemies who are suffering from injuries.
Benefit: You gain a +1 bonus on attack and damage rolls against grazed, wounded, or critical enemies.
For a grittier game in which wounds have a much larger impact, double the penalties imposed by the grazed, wounded, and critical conditions. Use this mode carefully, since it can cause a serious death spiral—in other words, the side that starts losing has tremendous disadvantages and is far more likely to die or need to escape. This adjustment also means that a spellcaster will always lose a level of spells she can cast when she drops from one wound threshold to a lower one, so the effects of wound thresholds on spellcasting are more predictable and stay consistent whether a character is at an even or odd level.