The Corruption of Lilith was the demonization of her human soul into a demonic spirit during the Fall of Man in the Garden of Eden, when sin entered the world.
History[]
After Lucifer was banished from Heaven in the first civil war, he was on Earth and travelled the planet. He tricked the angel on post Gadreel with cunning and sly, exploiting this weakness to make his way into the Garden. He killed Lilith, one of God's first humans, and twisted her soul into the very first demon. With this final act of defiance and insolence, God ordered Michael to cast Lucifer into the worst part of Hell, The Cage and God locked it with 66 Seals as locks that will release him if they were to be broken.
Aftermath[]
Lilith rules Hell as the strongest demon, and is eventually locked in the deepest part of regular Hell. Alastair becomes a White Eyed Demon around this point, and Adam and Eve are expelled from the Garden, and some time after, Eve gives birth to Cain and Abel.
Ultimately, Gadreel's actions indirectly leads to a sequence of cascading cause and effects and build up repercussions of God abandoning humanity, the creation of demonkind, and the progression of The Apocalypse.