|“||My advice: Steal something valuable, and fake your own death!||„|
Balthazar is a formerly antagonist, then he turns traitor and becomes an protagonist in the Season 6 of Supernatural. Balthazar faked his own death in the Apocalypse, and Castiel believed him dead. But Castiel was shocked when he read a young boy's soul and he found out that Balthazar was alive. So, Castiel went to see Balthazar but the rogue angel refused to fight. He displayed signs of cowardice, and arrogance, and he said that what was the point of continuing the War because "God wasn't coming back." Castiel said there was a point because Raphael was taking over Heaven and killing angels. Castiel told Balthazar he had to fight. Balthazar just said "Tell Raphael to bite me" and teleported off.
Castiel believed he had been abandoned by his friend, again, but to his amazement when Raphael and his angels showed up to attack, Balthazar smote Raphael with Lot's salt, damaging his vessel to the point where Raphael was now disembodied. Castiel thanked Balthazar, who was suddenly trapped in a ring of fire. The Winchesters demanded Balthazar give the boy's soul back to him.
Balthazar agreed, and then Castiel put in a word for him too, and the brothers released him.
Balthazar takes a dislike to Dean and Sam the moment he meets them, and Balthazar is often rude, obnoxious, arrogant and irritating. Balthazar says that Dean is a "hairless ape" and he also assists Sam with getting his soul back. He says that patricide will do the job. But Sam could kill Bobby because his own father needn't be the sacrifice. Fortunately, Sam gets his soul back before this can happen.
Raphael sends Virgil to get the brothers and so Balthazar gets together a spell in the Winchesters' room, throwing together Dead Sea brine, the bones of a lesser saint, and lamb's blood, and opens a gate to another universe. Balthazar throws the brothers in and later on he reveals the distraction was really so he could gather all of Heaven's weapons (when their guardian Virgil was absent, so Balthazar deliberately put the brothers in danger) and give them to Castiel. With the weapons, Balthazar and Castiel threaten Raphael, who flies off.
Later on, the Fate Atropos got pissed off because Balthazar, it transpires, went back to 1912 and unsank the HMS Titanic, saving everyone on board and stopping the natural cycle of Death. Atropos is out of a job, because when she went to Heaven, she was a joke. So, Atropos decides to give Castiel and Balthazar an ultimatum: she will kill everyone descended from the survivors, until Balthazar agrees to return History to normal. So, Balthazar does, but he acts rather lustful/flirtatious towards Atropos, causing her to firmly say "No" to him.
Balthazar, having reverted History, talks to Castiel about the War in Heaven and how it will affect the world. Castiel wanted to open Purgatory in secret with Crowley and he had told Balthazar not to tell anyone else, including Dean, where the gate would be opened, but Balthazar betrayed Castiel and told Dean. Then, Castiel found out and summoned Balthazar, saying there was a traitor. Balthazar attempted to talk his way out of it saying that it must be a Cupid. But Balthazar said Castiel would always have "little old me" to which Castiel said "Yes, I always will have little old you" and stabbed the traitor dead.