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

Betraying Shank

FEAT 6
ARCHETYPE
Activity 1 action
Archetype Twilight Speaker
Prerequisites Twilight Speaker Dedication
Requirements You are within melee reach of a target, but it is not in combat with you.

While your usual diplomacy is well intentioned, you know that sometimes those same skills will need to be turned to deception. In a flash, you draw a sheathed or concealed agile or finesse weapon and make a melee Strike. The target is Off-Guard against your Strike. You then roll Deception for initiative.

Pathfinder Adventure Path: GatewalkersORC