His wing is the special power given by his Angeloid core due to his request Deadelus Designed it to absorb any energy from his surrounding and turn it into Devil energy it helps in maintaining his reserve of magic energy . Another use it has that it absorb his magic energy upto certain quantity and compressed it to the extreme and released it on a single point in an instant. This has a cooldown period since his wing and Angeloid core get over heated and he can't use his wing for some time.