The Apocalypse started, Dean was constantly forced to say "Yes" to Michael and Lucifer was trying to convince Sam to say "yes" to him. While Sam and Dean were trying to remake the bond between them, also they were trying to make new connections and find new people who are willing to help them. After they found out The Trickster was actually the archangel Gabriel, he said by mistake another important information. All archangels have a vessel. Known or not. Even him. With this new information, they found Raphael's vessel but the man was completely ruined by the archangel. Castiel said Raphael wasn't even as strong as Gabriel or Michael so the damage might be bigger.