pf2e.fyi
From Pathfinder Adventure Path: Gatewalkers, which isn't enabled.

Star of Cynosure

ITEM 10
Price 175 gp
Usage affixed to armor
Bulk —
Category talisman

Activate (concentrate)
Trigger You attempt a Will save against a mental spell, but you haven't rolled yet
Requirements You have master proficiency in Will saves.

Found throughout Golarion, these star-shaped talismans of whalebone scrimshaw are carved by the Erutaki people from the Crown of the World. They are popular with adherents to the cult of Desna, who believe the talismans protect their dreams.

When you activate this talisman, you gain a +2 status bonus to saves against spells with the mental trait for 1 minute. On the triggering save, if the outcome of the roll is a failure, you get a success instead, or if the outcome is a critical failure, you get a failure instead.

Effect: Star of Cynosure

Pathfinder Adventure Path: GatewalkersORC