pf2e.fyi
From Pathfinder Adventure: The Slithering, which isn't enabled.

Rubbery Skin

FEAT 10
Archetype Oozemorph
Prerequisites Disturbing Defense

Your skin develops a malleable, rubbery quality. You gain resistance to bludgeoning damage equal to 2 + your number of class feats from the oozemorph archetype. You also gain resistance equal to twice that amount to extra damage from critical hits; if the resistance is greater than the extra damage, it reduces the extra damage to 0 but doesn't reduce the attack's normal damage.

Pathfinder Adventure: The SlitheringOGL