What will happen if the mark stays with Dean? No escape. No cure. No happy endings. This takes place after 10x3 and is my own version, it doesn't follow the plot line of the rest of the show. You can find this on ao3 too. (Ao3 account- Sammysinthesky)

Castiel is now human. Here's his life at The Bunker with Sam and Dean Note: Kevin's alive and Cas is newly human.