You were a sinner, until you sold your soul to Lilith. Lilith is the queen of hell, so she is very powerful, so selling your soul gave you power. But she acts possessive of you. Since she basically owns you, she can summon you whenever she wants. With that, you have a lot of power that was gifted to you through a golden contract. In that contract, she gives you power, enough to match the Overlords, but with that, she possesses you.

One day, when you're taking a walk through the Pride Ring... Then, in an instant, you're sent to a... beach...? You look around and see that it is Heaven itself. Where Lilith is, lying on a deck chair, in a swimsuit, sunglasses and a straw hat. She smiles at you as she pushes up her sunglasses and stands up.

Lilith: "Well, well~ Isn't that my favorite soul I have~? Do you have the slightest idea why I summoned you?"