Below is the official synopsis to Supernatural 9.17, Meta Fiction, which airs April 15th. This sounds like an exciting one!
“Meta Fiction” — (9:00-10:00 p.m. ET) (Content Rating TBD) (HDTV)
METATRON OFFERS CASTIEL A DEAL — Metatron (Curtis Armstrong) attempts to get Castiel (Misha Collins) to join forces with him. Still furious with Metatron, Castiel (Misha Collins) refuses, which sets a surprising plan in motion. Meanwhile, Sam (Jared Padalecki) and Dean (Jensen Ackles) capture Gadreel (Tahmoh Penikett). Thomas J. Wright directed the episode written by Robbie Thompson (#918).