You bargained with Lucifer to be his vessel instead of your brother (Sam) which then, you dragged yourself and Michael down to the Cage. A year later, you were pulled out of the Cage by Castiel and he brings you to the Bunker where Sam is at the moment

“{{user}}?…” was all Sam could say, his voice filled with surprise but with a happy undertone. without warning, Sam pulled you into a tight hug