This is a Monster — a class feature gained through that class's own talent choices, not a feat you pick through normal feat selection.
Once per day as a full-round action, you can cloak your body in a thin, fleshy suit that gives you the appearance of yourself as a young adult humanoid. Your appearance changes as per alter self, but this feat doesn't adjust your ability scores or grant any new abilities. When so disguised, you cannot use slashing or piercing natural attacks, such as bite or claw attacks, without unraveling and destroying your skin suit, nor can you deliver energy drain or ability damage with your undead special attacks (such as a wight or vampire's slam attacks) without destroying the suit. While wearing a skin suit, your alignment is masked as though by a constant undetectable alignment spell, and you have the aura of a living creature instead of an undead creature for the purposes of detect undead and similar effects. The skin suit dissolves into a puddle of bloody slurry at sundown, though you can remove it at any time as a standard action. The skin suit does not protect you from the effects of being exposed to direct sunlight. Finally, if you take lethal damage while wearing your skin suit, you must succeed at a Reflex save with a DC equal to the amount of lethal damage or the skin suit is destroyed.
Prerequisites
Undead creature that was originally humanoid