The CW has released an official description for “Byzantium” which is the Thursday, December 6 episode of Supernatural.
Here’s the write-up with new spoilers:
OUT OF THE DARKNESS – When Sam (Jared Padalecki) and Dean (Jensen Ackles) join forces with an unexpected ally, the outcome will alter the course of two lives. Meanwhile, Heaven faces an attack from a dark force, driving Castiel to make an enormous sacrifice to make things right. The episode was directed by Eduardo Sanchez and written by Meredith Glynn (#1408). Original Airdate 12/6/2018.
UPDATE: We now have photos! Enjoy!