When Dean goes to sell his soul at the crossroads to bring Sam back, someone else steps in to negotiate the deal. Cas did get a sign and it sent him off into the past to change things. AU from The Man Who Would be King and All Hell Breaks Loose.

Castiel and Merlin meet in the 21st century and become friends.

Shortly after Anna's fall from grace and rebirth, Castiel notes that she misses something important as a human, so he moves on to a certain action to remove this deficiency...