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

Elemental Bulwark

FEAT 5

Activity reaction

Trigger An enemy is about to damage you with cold, electricity, or fire, or with a spell that has the air, earth, fire, or water trait.

You call upon the corresponding elements of your suli heritage to resist the effect. You gain resistance 5 against the triggering damage.

Pathfinder Lost Omens Ancestry GuideOGL