pf2e.fyi
From Pathfinder Howl of the Wild, which isn't enabled.

Emergency Regeneration

FEAT 16
ARCHETYPEHEALINGPRIMALVITALITY
Activity reaction
Archetype Wild Mimic
Prerequisites Wild Mimic Dedication; you have deactivated a creature's regeneration for at least 1 round or have identified a creature with regeneration in combat
Frequency once per day
Trigger You're reduced to 0 hit points from damage that's neither acid nor fire.

You have battled against foes whose bodies naturally regenerate, and while yours doesn't do so all the time, it can happen in a pinch. You gain the effects of a 7th-rank Regenerate spell. At 20th level, you gain the effects of a 9th-rank regenerate instead.

Pathfinder Howl of the WildORC