In the eleventh season, Sam and Dean deal with the release of Amara/The Darkness, after Rowena's spell removed the Mark of Cain from Dean's arm. While Crowley's taking care of Amara, feeding her with souls, the brothers are, alongside Castiel, trying to find a way to kill The Darkness. In order to find out more about Amara, Castiel asks Metatron for help, and he says that in order to create the world, God had to sacrifice his sister, The Darkness. To face the most dangerous creature they've crossed paths with so far, the brothers ask for Lucifer's help. Lucifer claims he's the only one who can beat Amara, but in order to do so, he needs to possess Sam's body. When Sam refuses, Lucifer tries to kill Dean, Sam, and Castiel, but Rowena's spell seems to have sent him away. Later, it's revealed that Castiel said "yes" at the last second, and that Lucifer is now possessing his body.