A question about darkins

First, how many darkins have you met to observe that? We have only Aatrox, Rhaast and Varus as darkin champions. Varus is actually even more controversial than Aatrox.

Anyway, for your question. Aatrox was a golden winged ascended of Shurima that was beloved by shuriman folks. He was angel like ascended. Winged, shinning, honored. It was a form he admired and loved so much that he grieves his lost and tries to copy it, only to fail it miserably. In short, he tries to shape mortal bodies to reach his old winged form but he fails. It is the best he can do. That's why he is mad and bloodthirsty.