Although Kertein is angelic and has healing power still we don't know much about his attact style. Could it be he can summon and open the gates of he** like a demon!!
@Hanni Graham u are... cus where the he** did that even come from, you deff ain been paying attention to think heavin nd da** he** is involved when demons ain even a thing here
he he called his attack black swamp, so it could be something similar where he liquifies the ground into something murky to ensnare his victims. But this move works only on weakened foes or folks who can’t really fight back like earthquake
