resurreccion
Resurrección is the ability of an arrancar's zanpakutou (a type of weapon in Bleach, often a sword) of either disappearing or transforming itself, while giving the wielder a monster-like appearance and special powers. This transformation is into a form reminiscent of when they were still a basic hollow, before becoming an arrancar. Once activated, resurrección must be undone via sealing the powers away again, if not done properly, the Arrancar will lose the ability to preform resurrección, and will lose their hollow abilities also.
For example, when Ulquiorra Cifer is in resurrección mode, he gains bat wings.