Demons

Demons live in a parallel existence. Once demons and Sleepers had battled each other until the demons were locked in their world due to a prophecy. Since then they have been waiting filled with bitterness to conquer the universe as in the good old times.

The demon Fate is the leader and similar to a living god. There had been a war between Sleepers and demons thousands of years ago. It had been settled with a bet between the demon Fate and the Father of Gods. The bet implys that the one shall rule the universe of which substitute's is victorious.

That's how the prophecy arose and the demons were locked into their parallel existence until the prophecy's end fight happens. Fate started to influence Sleepers because of this betrayal. He tries to pull them onto his side to expidite the fight for the universe's hegemony. His main goal is to eliminiate all Guardians of Fate at the same time due they are the key why demons have been locked into the parallel existence.