I'm looking for this particular fic that I don't quite remember what the title or who the author is. In this fic, Michael and Lucifer are mates. When Michael forced to seal Lucifer into the cage, he fell into depression. As the time passed, he didn't take it anymore, and so he tore his own grace, become a fallen, and reincarnate into a human named Dean Winchester. It's bottom!Michael/bottom!Dean.