Supernatural (Season 5)

 The fifth season revolves around the fight to stop Lucifer and save the world from the Apocalypse, inspired by events in the Book of Revelation. Throughout the season, while Castiel searches for God, Sam and Dean battle both angels and demons as they fight their destiny to become the vessels of Lucifer and Michael, respectively. One way they attempt to stop Lucifer is to retrieve the Colt from the demon Crowley and kill Lucifer with it, but this fails as Lucifer can't be killed by the Colt, and they lose fellow hunters and friends Jo and Ellen in the process. Their loss, and the revelation that God will not help stop the Apocalypse, drives Dean to agree to act as the vessel of Michael, but, ultimately, he doesn't go through with it. Instead, Dean kills the angel Zachariah, who has been tormenting the brothers all season. Michael ultimately takes Adam Milligan, the newly resurrected half-brother of Sam and Dean, as a vessel instead. Unable to defeat Lucifer, Sam and Dean, with information from the Trickster, revealed to be the archangel Gabriel, and with help from the demon Crowley, decided to collect the rings of the Four Horsemen of the Apocalypse, including Death, which act as the key to Lucifer's prison. The concept of destiny versus freedom, choice, and free will plays a large role. Throughout the season, Dean, Sam, Castiel, and Bobby each have a crisis as they near giving up. However, through each other's support, they continue forward until the end. It is also notable that Dean and Castiel have an ongoing friendship during this season, while Dean and Sam initially grow further apart. In the end, Sam allows Lucifer to possess him and he kills Bobby and Castiel, who is now human. Sam then manages to regain control, thanks to his bond with Dean, and throws himself (while possessed by Lucifer) and Adam (possessed by Michael) into the Cage to trap Lucifer once more. Castiel is resurrected by God and, more powerful than ever, resurrects Bobby and then returns to Heaven to restore order. Dean returns to his old girlfriend Lisa to live a normal life. Sam is next shown mysteriously free of the Cage, watching his brother eating dinner in the house with Lisa and her son Ben.