pf2e.fyi
From Pathfinder Lost Omens Divine Mysteries, which isn't enabled.

Flash of Omniscience

FEAT 18
Activity free action
Archetype Mortal Herald

Trigger You turn begins.

You briefly see the world as your deity does, recognizing the truth of those around you for a moment. You spend a Mythic Point to immediately learn the resistances, weaknesses, and immunities, including the amounts of the resistances and weaknesses and any unusual weaknesses or vulnerabilities of a single creature you can see.

Pathfinder Lost Omens Divine MysteriesORC