Then let's keep that trend going. Look, he's arrogant too, right? I think he'd name himself in a way that shows his achievements of absorbing and unifying all sins into himself. At first, I thought maybe something like Duke Monad would be okay, but... I really don't like that name, still it is a name and it's your character, so you can pick it if you want; it means something like "the total of all things" so, it fits.
But, honestly, I am sort of a fan of Duke Henosis. It's Greek. I think it means something like "union with the mystical" or "mystical unity" or something like that. I offered. Your choice.