Creature Abilities
Source Alien Core pg. 208
The following creature abilities are listed here because they are shared by many creatures or are highly complex. The statistics for individual creatures might alter the traits, the number of actions, or other rules of these abilities. Anything noted in a specific creature's stat block overrides the general rules for the ability below. In these abilities, “monster” is used for the creature that has the ability, to differentiate it from any other creatures the ability might affect.
Ferocity [reaction]
Source Alien Core pg. 209
Trigger The monster is reduced to 0 HP; Effect The monster avoids being knocked out and remains at 1 HP, but its wounded value increases by 1. When it is wounded 3, it can no longer use this ability.