The scenario that I'm looking for here involves two people: one is a powerful galactic tyrant, eager to show his power to the galaxy. This would be played by you. The other is the poor being that he chooses to be his most powerful servant, and his steed.
He would choose this being for reasons of his own: perhaps she was a beautiful girl from a conquered planet who caught his eye, or a rival/brother/sister whom he defeated, or a first love who rejected him. Regardless, he has used his cosmic power to remake his slave as a powerful cosmic being in their own right, strong and able to travel through the stars faster than the speed of light.
And why has he done this? So that his slave might pull his resplendent chariot into battle, or whenever he wants to show off. Naturally, he would also enjoy taking his pleasure from this slave when the feeling strikes him. She would be tended as well as any treasured pet, but would also be treated as a pet; her clothing if he chose to dress her, would be more for decoration than actual covering; after all, anyone who can fly through the cold vacuum of space would have little need of clothing for protection.
If you are a comic book fan, you probably recognize this as being a pervy, sexualized take on Galactus and the Silver Surfer. I imagine I'm the only person who might get off on this, but I thought I'd ask anyway, to see if there were any other deviants about.