This is Rood, in his HyperGod form. He’s the HyperGod of Protection, due to his huge wish of protecting everypony that needs to and to the feeling of avenge his dead friends.
 
He doesn’t have a horn, but still can use magic. Why? Well, because HyperGods do not need a horn to process magic, as they can do it directly from their brain. That’s why he can summon the portals he uses to fire nebula beams and lift his hammer, and do everything else he was able to do before turning to a HyperGod. He can still switch back to his original unicorn form though.
 
Art by the awesome “Gutovi”:gutovi.deviantart.com. Check him out! You won’t regret it!