Season synopsis
Contains spoilers for this season and earlier seasons.
Castiel’s claim to be God collapses when his body cannot contain Purgatory’s power. Death helps him return the souls, but Leviathans remain inside and take control of his vessel. They escape Castiel's collapsing body and begin using human hosts, while Sam and Dean try to contain their attacks. Sam still suffers hallucinations tied to Lucifer's Cage, and Bobby helps the brothers investigate the Leviathans until Dick Roman's corporation becomes central to their plan.
Dick runs Richard Roman Enterprises and acquires SucroCorp, its food-company subsidiary, to distribute an additive that alters the human food supply for Leviathan consumption. The brothers enlist hacker Charlie Bradbury and prophet Kevin Tran as they search for the weapon that can kill Dick. Bobby is shot by Dick and dies; after returning as a ghost, he asks Sam and Dean to burn his flask so he will not become vengeful. They honor his request before assaulting SucroCorp.
The weapon requires a righteous person’s bone and blood from three supernatural leaders. Crowley pretends to bargain with Dick but gives the Winchesters his own blood. At SucroCorp, Kevin tells Sam the lab is the target, while Dean and Castiel identify the real Dick among his decoys. Dean kills Dick with the prepared bone. Dick’s death sends Dean and Castiel to Purgatory; Crowley arrives with demons and takes Kevin, leaving Sam alone at SucroCorp.