A facestealer doppelganger can steal not only the appearance of a humanoid creature, but also their very personality. You have inherited some of this power.
Prerequisites
Monstrous Bloodline (Doppleganger), Change Shape, bloodline level 1st.
Benefit
Whenever you successfully maintain a grapple against a humanoid creature, instead of dealing damage to the creature you are grappling, you can instead deal 1d3 points of Charisma damage. You gain an insight bonus equal to the number of Monstrous Blood feats you possess on Deception checks to disguise yourself as any creature you have damaged with this ability.