An Evil Bastard on Row

"Just wondering, why me?" I asked. "I mean, of all the people to give this gift, why would you choose to give it to me? I mean no disrespect but, I would think that I am the last person anyone would want to give that kind of power."

"The last person a human might think to give it to, but I am hardly human. I watch everything, see the infinite, gaze upon the eternal, and you have no idea how boring it can all be. Giving someone like you, someone who delights in self-indulgence, someone who as an artist's flare for torment and a deep seated cruelty at the bottom of their black heart, it makes life interesting.
"Though, be warned, there is a catch." said The Darkness.
"There always is." I sighed. "What is it? I mean, I am pretty sure that I was already on the express bus to Hell. So it cannot be my soul or any of that garbage."
"Oh no, nothing like that. It is just that, to make things interesting, at some point a few years down the line, at least seven but maybe as much as a thousand years into your reign of terror, but at some point there will be a solar eclipse that lasts for a day and a night, comets will dance and a new constellation will be born to signal the birth of a hero who will have the power to bring an end to your tyrannical rule and cast you into the Hell you so keenly pointed out you were heading anyway, only if you accept, you will arrive with a benefits package as opposed to your current status which was an eternity as, well, lets just say that its designed for you to find it unpleasant."

"So, what is it you want me to do exactly?" I asked.
"We need someone to take the role of a Demon King. We set you up with a new body in a new world, could be almost identical to this one, could be different. Can't say when your consciousness will kick back in, best guess is either at birth or at eighteen, depending on nether currents and quantum tides in the transplanar junctions. Regardless. Your job from that point on will be to spread The Antitheon's influence. "

"The Antitheon?" I asked. "What is that?"
"The easiest way your mortal mind could understand it is as a club for outcasts and misfits among the things you would think of as gods, devils, and things that are difficult to categorize at the edges of the cosmos. They have decided to form a corporation to further their mutual desires to bring the universes under new management. That is where you come in.
"Start small, just take over the world, collect the population's souls. Then open gateways to other dimensions and conquer them too. Feed on the psychic energies of your minions, experiment with arcane powers and cosmic forces. Just have fun."

"Where do I sign up?" I asked.
"Just step through the portal. Walk into The Darkness." said the swirling black void.

I shrugged. With nothing to lose. I stepped through the portal that takes me to...