Most creatures have a certain maximum health and stun resistance which never change.
Stun resistance acts as a divisor; a stun resistance of 2 halves stun duration.
Some creatures also have an instant death threshold, the ramifications of which are discussed in the relevant section.
When a creature is first spawned, its current health is set equal to its maximum.
Except a few cases, health does not regenerate during a cycle.
Slugcat recovers all lost health at the end of a cycle, and most other creatures recover 25% health.
When violence is enacted upon a creature, its current health may be reduced and it may be stunned or killed, depending on the properties of the violence.
Although Slugcat has health, it can only be reduced by Spears or Lilypucks.
When Slugcat is attacked by most creatures, they simply have some random chance to die.
Causing a creature to die is not as simple as reducing its health to 0; creatures can live on at negative health.
Most creatures can die one of four ways: bleedout, instant death, quick death, and direct death.
Bleedout
When a creature's health is below 0, they enter bleedout.
Each frame that a creature is in bleedout, they have a chance to die which depends on their current health - the further below 0 their health is, the most likely their death.
Bleedout never guarantees a creature's death, although death becomes arbitrarily likely with enough time.
Most creatures with health can bleed out if they do not first die another way.
Batflies, Coalescipedes, Leeches, Garbage Worms, and Slugcat cannot bleed out.
Instant death
If a creature takes more damage than their instant death threshold from a single act of violence, they suffer an instant death.
Not all creatures can suffer instant death, but most smaller creatures, including Slugcat, can.
Most instant death thresholds are around 1.0 - the same as the damage dealt by a Spear thrown by Survivor.
Quick death
If a creature receives violence which leaves their health at zero or less, they may suffer a quick death.
For most creatures, as health varies from 0% to -100%, the chance that violence causes a quick death varies from 33% to 100%.
Dropwigs' chance of quick death varies from 66.5% to 100% instead.
Slugcat can suffer a quick death if damage from Spears or Lilypucks accumulates to 1.0 or more - in which case they have a 100% chance to die regardless of health.
Any death not falling into one of the above categories is a direct death which bypasses health and resistance.
Following are some examples of direct death.
If an air-breathing creature runs out of air underwater, they may die (although Slugcat first enters a drowning state).
If a creature that cannot fly falls below the lower bound of a room, it dies.
If a creature that can fly falls below the lower bound of a room while stunned, it dies.
If the mass of all Coalescipedes grabbing a creature exceeds that creature's mass, the creature dies.
If a creature collides with the core of a mobile Rot cyst while at least one of its tentacles is holding that creature, the Rot begins digesting them. After 1 second of digestion, the creature dies.
If a creature is caught by a Leviathan's bite, it dies.
Once the pull of Worm Grass on a creature becomes strong enough, the creature dies. Some creatures, like Rain Deer, are grabbed but not pulled by Worm Grass.
Once a creature is held by Proto Long Legs for long enough, it dies.
If a creature contacts the core of a Giant Jellyfish, it dies.
If a creature is within 350 units of a Singularity Bomb when it detonates, it dies.
If a creature is sufficiently submerged in the acid of Garbage Wastes, it dies (although Artificer may survive if they aren't overheating).
If a creature is stunned for long enough while sufficiently hypothermic, it dies. Severe hypothermia itself can cause such a stun.
The following are only applicable to specific creatures:
Slugcat dies if they are dragged into a creature den.
Slugcat dies if they impact terrain with enough velocity while moving downward.
Scavengers die if their health is reduced to below 0 after being struck in the head for at least 0.5 damage.
Giant Jellyfish die if they receive more than 1.0 explosion damage at once.
Artificer dies if they perform too many bomb jumps or concussive blasts while overheating.
Trivia
Internally, health actually starts at 1.0, or 100%, for all creatures. What is described here as health for most creatures is the effective health when accounting for baseDamageResistance, which divides all incoming damage.
Slugcat
Overseer
Green Lizard
Pink Lizard
Blue Lizard
White Lizard
Black Lizard
Yellow Lizard
Cyan Lizard
Red Lizard
Salamander
Batfly
Squidcada
Snail
Red Leech
Sea Leech
Pole Plant
Monster Kelp
Garbage Worm
Scavenger
Vulture Grub
Vulture
King Vulture
Infant Centipede
Adult Centipede
Red Centipede
Centiwing
Grappling Worm
Hazer
Lantern Mouse
Coalescipede
Big Spider
Spitter Spider
Miros Bird
Brother Long Legs
Daddy Long Legs
Rain Deer
Eggbug
Dropwig
Infant Noodlefly
Adult Noodlefly
Jetfish
Leviathan
Guardian
