Goodnight, Grace Asala manages to open up the rift one last time, and people are prepared to go in and fight Satan and somehow save Castiel — but Cas comes stumbling out of the rift, successful.
Lucifer is caged and the rift can snap shut.
Castiel tries to heal Sam, but Sam insists that Dean needs it more or else he's going to die. Cas gives up the last of his remaining grace to heal Dean, rendering him effectively mortal.