He is hostile to the player, thinking that they are a demon (most likely he was trapped in the stasis before nephalem came to exist). Erelus's wings, just like wings of his soldiers and Haziael, are black in color, apparently a result of long separation from the Crystal Arch. In combat, he has Arcane Enchanted, Frozen, Fast and Teleporter affixes. Until killed, he will summon more and more Timelost Angels to join the battle.