Castiel, as far as I know. Here is the official description:
“The Born-Again Identity”
MISHA COLLINS RETURNS! — Lucifer (guest 星, 星级 Mark Pellegrino) drives Sam (Jared Padalecki) to the breaking point and Sam ends up in a mental hospital. Desperate to save his brother, Dean (Jensen Ackles) calls every hunter he knows for help. One of the hunters gives him the name of a healer who turns out to have a very familiar face (guest 星, 星级 Misha Collins). Robert Singer directed the episode written 由 Sera Gamble (#717).
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