Season 7 opens with Dean, Sam and Bobby facing Cas who is acting like the new God. He wants them to worship him - he seems to have gone mad with the power...
Cas doesn't kill them though. He disappears and goes off to Heaven to smite Raphael's angels for siding against him. Cas also tries to win followers on Earth by helping humans but the souls inside him are affecting him.
Sam is not in good shape. He's having visions of the time when he was in The Cage with Lucifer tormenting and torturing him.
Dean uses Crowley's help to conjure a spell to trap Death, like Lucifer did, to force Him to do their bidding, to kill Cas. Death is very displeased with them but he's chained up. However Cas appears and frees Death and then disappears. Death agrees to help them to remove the souls from Cas as He thinks Cas is acting way above his pay-grade and he advises them that they need to perform the same ritual that Cas did. He even arranges for an eclipse, which is required.
Cas comes to realise that the souls are corrupting him and can't be contained so he agrees to undergo the ritual. The Boys perform it and the souls leave Cas and the portal closes and Cas seems fine but then he tells them that the Leviathans are still inside him.
Written by Spnfanforever