The Esper Saga
Diablos is the Esper of Darkness. He appears as a pitch-black humanoid with horns and leathery wings, only his eyes forming a contrast with a curious inky white darkness. Diablos can slip between worlds and travel freely, and he can additionally dissolve his form into shapeless darkness – though in that form he can only observe and talk, not interact with anything. Diablos’ intentions are cryptic, but he seems to work in league with the Emperor. He is the father of Angela Treagent, and he is suspected to keep a secret Sanctum somewhere.
Demons did the acts said to be done by Diablos, in the first age.
He was one of few who didn’t (Diablos quote:) cower in the faked-esper haven, the sanctums.. Mortals attacked him, he annihilated them. The ignorant sons and daughters tried to stand against Diablos, which resulted in the death of the first Esper, even while only being half, by an other Esper.
Diablos was sentenced to a 100 years of confinemeant, with his powers sealed away. “Shortly” after his return he witnessed what the other espers did to a son of the Espers… Sealing him away, only because they couldn’t kill him. Infuriated by the hypocrysity, he joined forces with Siegg to show the other Espers what he learnt in his time of punishment, “With Great Power Comes Great Risk”. In his mind only he truly understood the words that had been spoken to him: The Rules of the Espers must be protected, for both the worlds!