pf2e.fyi
From Pathfinder #177: Burning Tundra, which isn't enabled.

Stalwart Mind

FEAT 8
ARCHETYPE
Activity reaction
Archetype Mammoth Lord
Prerequisites Mammoth Lord Dedication
Frequency once per day
Trigger You fail a Will save.

When necessary to avoid a magical compulsion or curse, you can be as stubborn as your megafauna companion. Attempt a new Will save against the triggering effect.

Pathfinder #177: Burning TundraOGL