So far we see that Asta when transforming into Black Asta can fly and gets his skin covered with some black sustance in parts. But what others powers does he get when transforming? Does he get some protection or enhanced skills? Or is it just the possibility of flying?
Apart from the ability to fly, Asta's speed and strength are greatly increased when he enters his anti-magic state.
Asta also gains the ability to sense strong mana. Actually, its more like his Black Asta form is automatically drawn to strong magic. And depending on how much Anti-magic he channels through his body, the overflowing energy erodes magic near him.