pf2e.fyi
From Pathfinder Book of the Dead, which isn't enabled.

Frighten Undead

FEAT 6
Activity 1 action
Archetype Undead Slayer
Prerequisites Undead Slayer Dedication; trained in Intimidation

Your very presence chills creatures of the night down to their core and you can use the spiritual power and faithful life force of religious verses to frighten even mindless undead. Attempt to Demoralize an undead target using your Religion modifier instead of your Intimidation modifier if it's higher. If you use your Religion modifier, the Demoralize action loses the emotion and mental traits, as your faith connects to the undead on an instinctual level.

Pathfinder Book of the DeadOGL