 With his powers restored, Castiel helps Claire find her long-lost mother, but although Amelia sacrifices herself to save Claire, Claire accepts that the Winchesters and Castiel meant well, even speculating that she will become a Hunter herself.When Rowena – Crowley's long-lost mother – casts a spell to remove the Mark, she also casts a spell that causes Castiel to attack Crowley while she escapes, leaving Castiel driven by a greater rage to the point that he kills two angels until Rowena is forced to cure him.Faced with the threat of the Darkness – revealed over the course of the series to be God's 'sister', sacrificed to create the world – Castiel agrees to act as Lucifer's vessel when Lucifer claims to be the only one with the power to defeat the Darkness, since God is absent and all other archangels are dead or insane.