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

Mask Freeze

FAMILIAR ABILITY

When in mask form, your familiar can hide its obvious supernatural qualities to pass as a simple, unassuming mask. It doesn't need to Impersonate to fool a passing glance, and it gains a +4 circumstance bonus to its Deception DC against an active observer Seeking or otherwise studying it.

Pathfinder Lost Omens Character GuideOGL