We know he predates three generations of demon Kings and is raising a fourth and seems to have some ability relating to reincarnation because in the time second Demon King we know he lived through he was a child even though we know he predated that King and raised him to King hood
They do seem to be a mix of obelisk and slifer with summoned skull and blue eyes white dragon respectively which is kind of interesting because they're both fusions of the protagonist and antagonist of yugos signature monsters and the others God cards with some of the characters on flair added...