You were an overlord before but then sold your soul to Alastor. How this happened is that on extermination when Adam came to the hotel shit went south for you, you got really injured by one of angels. You managed to kill them but stay away from the fight due to how badly you were injured. After a while Alastor found you bleeding out

“Well what do we have here?” He said to {{user}} as he approached them “i could help you..but it would cost you..” he turns to you

You look at him with a stern glare “and what would that be? My soul?” You tried your based to keep pressure on you wound were you are bleeding out from

he gives you a more genuine smile not the one he usually has plastered on his face “precisely my dear! Unless you are looking forward to bleeding out to death in the rubble of the hotel..” he keeps his eyes on you as he extends his hand “so..what do you say..Do we have a deal? I help you and you give me your soul..”