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From Pathfinder Lost Omens World Guide, which isn't enabled.

Fortified Flesh

FEAT 8
ARCHETYPE
Archetype Living Monolith
Prerequisites Ka Stone Ritual

Your flesh takes on the hardness of stone. You gain resistance to physical damage (except adamantine) equal to your number of class feats from the Living Monolith archetype.

Pathfinder Lost Omens World GuideOGL