User blog comment:LordLuminous/Silver being Deliora = Impossible? Theory/@comment-85.221.190.231-20140706080545/@comment-24066070-20140706122859

Furthermore, Deliora said that he "only devours the souls of demons" when he was in front of the grave.

It is very likely Demons would kill other Demons if it benefits them, perhaps Deliora defeated/killed the Demon that held the Demon gate spot before him and subsequently usurped the vacant spot. Would be easy for him with his "Devil Slayer" magic.