Lucifer

Lucifer, also known as The Devil, Light Bringer, The Morning Star, and Satan, was the second of the four Archangels created by God and was his favorite son. He is also a fallen archangel and the first fallen angel. He is the original ruler of Hell and the creator of demons, seen by them as a father figure and their god. As the second-born Archangel, he is the younger brother of Michael, and older brother of Raphael and Gabriel.

According to Bernael, Lucifer is, or at least was, God's favorite and most beloved celestial, but when God asked for all angels to bow down to humanity, Lucifer refused both out of jealousy and wounded pride over being commanded to bow to what he saw as a broken, flawed, and murderous species and no longer feeling he was God's favorite creation. He waged a war against God but was eventually cast out of Heaven by Michael, and later banished to Hell by Michael, both times on God's command. All of Bernael's actions were motivated with the goal of eventually releasing Lucifer from his cage in Hell.

Like all other angels, Lucifer must have the permission of a strong enough human to use as his vessel, as he can not forcefully possess a person. Being an archangel, Lucifer possesses much more power than any normal angel, every pagan god, and also every demon and species of monster, most of whom deify him. But his power causes regular vessels to decay and required to drink vast amounts of demon blood.

Eventually, he was finally freed and allowed to roam the Earth when Bernael and Abaddon performed an ancient ritual to free him.

Freed from his cage, he took action to bring about the Apocalypse and cleanse the Earth (aka "The last perfect handiwork of God") of human beings (the flawed creation). He was eventually sent back to the cage when Markus Hollands takes back control of his body and Rebecca opens the cage door, only for Markus to jump in, locking both Lucifer and Markus in the cage.