Abyssal Void Beast
When he looked into the mirror he saw that he had grown a second pair of horns underneath his other pair.
The two pairs looked like crystal but were so black that he had to look closely to realize that the shine on them was more than a reflection of a glossy surface like the horns of certain cattle.
His eyes had changed in a very strange way as well, before they had actually been fairly normal looking eyes but with sclera that became more black with each evolution.
Now he saw his crimson irises has changed from a circle to a bizarre star shape.
The way his wings had looked before were no different from bat wings but now he saw that the muscles in what would be considered rhe bicep were much thicker and the thumb at the joint of his wing seemed to have gotten shorter with a sharper claw.
He also saw that his tail was significantly longer like a bull whip with an arrowhead tip.