|You think his friends just called him Yellow Eyes? He had a name.|
This article is about a canonical individual whose real name is unknown, and is known only by a conjectural title, nickname or alias.
After locating Balthazar, Castiel finds him possessing this man though it is unknown if he possessed him before or after he fled Heaven during the Apocalypse. While Castiel recognizes Balthazar immediately, he knew who he was looking for and angels can tell who each other are so it is unknown if Balthazar took possession of this man to hide out on Earth or already had him as a vessel beforehand.
After discovering that Balthazar has betrayed him, Castiel teleports behind him and stabs Balthazar through the back with an angel blade, killing Balthazar and his vessel. It is unknown what happened to the vessel's body after that, but it was likely left abandoned on the floor of Crowley's lab as it seemed no one had gone there between everyone leaving after Castiel declared himself God and his return to send the souls back to Purgatory.