After spending four long, horrific months in Hell, Dean Winchester is miraculously raised from the Underworld and resurrected by an angel of the Lord God Himself named Castiel, one of several angels who appears throughout the season. After Dean reunites with his father-figure friend Bobby and his brother Sam, the rest of the season follows the brothers, with the help of their friend Bobby, as they work with Castiel and his subordinate and friend Uriel to stop Lilith's plan of breaking the 66 Seals, which would allow the fallen archangel Lucifer himself, AKA Satan or The Devil (who was once the favored angel of God but rebelled against Heaven for not serving humans and therefore was cast down), to be released from his cage in Hell.