 After killing Rowena, apparently the only person capable of re-opening the Cage, Lucifer spends some time re-establishing his power base in Hell while acting as Castiel to interact with the Winchesters and follow their research into Amara, but his true identity is revealed after the Winchesters attempt to travel back in time to recover a Hand of God from a submarine before it sank in 1943.Castiel is able to regain control long enough to explain the situation to Sam and to stop Lucifer killing him.Dean subsequently returns and banishes Lucifer, vowing to find a way to free Castiel from his control.