The First Fallen Angel
Lucifer was one of the original Archangels of Heaven, widely believed to be the greatest of them and the closest to God. The Heavenly Host was shocked to its core when Lucifer rebelled against his creator, leading an army of like-minded angels in a massive revolt against Heaven that became an all-out spiritual war. In time, Lucifer's forces were defeated, however, and he and his rebels were cast out of Heaven. Most of the angels simply fell to Earth, becoming human, and many eventually became a new class of demon. Lucifer, however, was not allowed to roam free.
Heaven, Hell, or (some say) both together locked Lucifer in a spiritual cage, sealing it tightly with divine magic. To open this cage, sixty-six magical seals would need to be located and destroyed. Beyond that, the cage itself was placed in the deepest, most well-guarded pit of Hell. There Lucifer languished for millennia, transformed over time into a powerful demon.
Despite his origins, Lucifer became quite a romanticized figure by some--particularly those who were not especially fans of Heaven. Prophecies and myths would rise around him, and in time, some factions of Hell would come to see him as their destined leader, setting plans into motion to free Lucifer from his imprisonment. Chief amongst his would-be followers was Azazel, a powerful demon with yellow eyes.
Both Heaven and Hell developed prophecies concerning Lucifer, but the most concerning of these foretold a possible apocalypse, wherein The Archangel Michael would face Lucifer in a final battle for the fate of humanity. According to Heaven, Michael would be victorious, and the battle would only destroy one third of the life on Earth. Hell believed that Lucifer would win, though casualties were still likely. It is unknown whether either of these prophecies indicate what role the other Powers That Be might play in Armageddon.
Logs featuring Lucifer: