ffXII main bad guy

[Ultima Shadow]

My villain:

Long ago, a gigantic, terrible creature raised from hell(or something like that) to destroy the nations of the world and turn the world into a world of demons. However, a powerfull blackmage called Vollder defeated the creature and send it back to hell(or where ever it come from).
But the demonic creature cursed Vollder during the battle.
Vollder knew that he had to do something, or he would die.
The curse tortured Vollder for years... but then, one night... a messenger from Hell(or whatever the place is) come to Vollder and told him that "the demonic creature" would cure the curse if Vollder went to hell(I call it that from now on) and swore to serve the "demonic creature" in 13 years.
Vollder accepted the deal and went to hell. But when Vollder had been the "demonic creature's" slave for 13 years, the "demonic creature" refused to set Vollder free. Another battle started but this time the deamon prevailed. Just as the demon was about to finish off Vollder, Vollder used all his magical power to let his spirit leave his body and then colide with the the "demonic creature's" spirit. Vollders spirit tried to kill the demons spirit and trough that take controll of the demons body. But instead the 2 spirits merged into 1. The demon and Vollder became one. Vollders painfull memories and the demons hatered.

The spirit of Vollder and the demon could posses both Vollders and the demons body.

The new, evil spirit used Vollders body in the world above... and the demons body in hell.
The demons hate merged with Vollders memories make the spirit to want everyone to suffer as much as Vollder did.

Vollders look: Long, black hair, black cape, blue red and black clothes and a face that... doesn't look very nice.

Look of the "demonic creature": Anything as long as it's cool.

I think I could have come up with something better... but I'm to lazy.