So, according to most Abrahamic mythology, Levithain was the only Sin to not have been a fallen angel. It's stated that Yahweh couldn't actually slay Levithain, and so he simply banished her to The Abyss.
She's also clearly the Abrahamic Jörmungandur. She is also said to basically be Tiamat, according to the book of Epoch
All this to say my interpretation of Levithain is that she existed far before Yahweh and his Ascension to power. She ruled unchallenged in the great depths of the sea and the Aether.
He had a counterpart named Behemoth, basically the land equivalent. (He'll get his own design page, but he doesn't show up till much later)
(They are also kinda similar relationship to Brynphoet and Baphomet)
Levithain within my story/lore is Tiamat and Jörmungandur. She is far older than Yahweh and far more powerful as well. Surviving the many different pantheons that have ruled the mortal world. He holds wisdom that far exceeds any other Deamon.
However, after the death of the Norse gods, Levithain laid weakened, and so Yahweh sealed away a great deal of Levithain's power and cast her into the Abyss.
So before the Morningstar fell, Levithain writhed in the pit. He envied the freedom of all those eldritch things that swam around them in the abyss.
She existed as a living Whale Fall.
Then, when the Morningstar and his rebellion fell, Levithain became the very foundation of the pit. Her flesh calcified to brimstone, her blood ran red hot and pooled in lakes of fire. She was made the prison to hold those who Yahweh say his enemies.
Lucifer, in an appeal to Levithain, made a deal with her. He would separate her soul and body, allowing her freedom from the constant pain if Lucifer he could retain control of the body.
This allowed the sovereign of hell to hold some maleable control over his new prison.
Levithain now swims the Abyss, and any soul left unprotected will most likely fall victim to The Maw of Levithain.
