pf2e.fyi
From Pathfinder Lost Omens Cheliax, Infernal Inheritance, which isn't enabled.

Forged in Fire

REACTION
Activity reaction

Trigger You take fire damage
Frequency once per day

Effect You gain fire resistance equal to half your level (minimum 1) against the triggering damage.
Pathfinder Lost Omens Cheliax, Infernal InheritanceORC