Season synopsis
Contains spoilers for this season and earlier seasons.
Lucifer walks the Earth after the final seal breaks, and Sam and Dean learn that they are intended vessels for Lucifer and the archangel Michael. The brothers initially separate because Sam blames himself for releasing Lucifer, while Dean is drawn toward the angels' plan. They reunite to hunt and look for a way to stop the Apocalypse, meeting the demon Crowley and pursuing the Horsemen's rings. As disasters spread, their cases and alliances become part of a larger effort to stop the Apocalypse before Lucifer can secure his role in it.
The angels press Dean to accept Michael, while Sam decides that becoming Lucifer's vessel may be the only way to contain him. Bobby, Castiel and the brothers gather the rings and learn that Death may help them reach the Devil's Cage. Sam and Dean argue over whether either should make the sacrifice, then agree to Sam's plan: he will say yes to Lucifer, regain control if he can, and take Lucifer into the Cage. Dean promises to seek an ordinary life with Lisa if Sam does not return.
Lucifer takes Sam as his vessel and overpowers Dean at Stull Cemetery. He disintegrates Castiel and snaps Bobby's neck, but Sam sees a toy soldier in the Impala and regains control. Sam opens the Cage and jumps in with Lucifer; Michael, using Adam as his vessel, is pulled in too. Castiel reappears, heals Dean and revives Bobby, while Sam's fate remains uncertain. Dean keeps his promise and goes to Lisa. In the final image, Sam stands outside her house, but the season does not explain how he returned from the Cage.