Larian Studios Forums Divinity: Original Sin 2 Divinity - Original Sin 2 - General Mechanically, is Fane the best story character?

Nah, that's bullcrap.
The moment you take it off, you revert to his undead form and regain his racial bonus of Initiative and Critical% + Play dead.

The best way to use the mask is to start turn one, Blood Ritual and unequip it for no AP to enjoy the whole AP, Damage, Initiative and Critical% Bonus.