Aiden is a being sharing the homeworld of Kayle and Morgana. When Aiden was born, his proficiency with magic was limited and weak -- combined with his abnormal physical features, Aiden was looked down upon as some sort of worthless mutation. But Aiden would not be dismissed, so easily. Eventually Aiden became a warlord -- infamous for ripping the wings off his captives. His influence spread so far over the world that drastic measures were taken to remove Aiden from power. The mission almost ended in failure, but Kayle and Morgana were the ones who succeeded in subduing the warlord -- though many lost their lives in the process.
Thousands of years later -- Aiden has broken free. And he's hunted his jailors all the way to Runeterra.
Unlike Kayle and Morgana, Aiden is AD bruiser in nature. He uses his tremendous wings to close-in on, capture, and crush his enemies. His very limited magic capabilities are bound to being buffs that effect only himself, raising his speed and attack.
I wanted to fulfill a "devil" or "demon" character concept -- but I wanted to avoid an overly evil archetype for appearances. I thought it would be neat to see the trope as a mirror to Kayle because Morgana only fulfills the need half-way. Going off of being something of an opposite, I also believed it would be important for Aiden to be more physically powerful as opposed to being magically inclined. So his wings are more bulky and muscled in comparison to Kayle's.