"Demons. Beings cast out of creation who have no words for moderation. Predecessors to mortals. They simply exist, driven by instinct , disrupting the functioning of Mundus whenever they can."
-Scripture passed down through generations of High Priestesses
Phoebe had grown up surrounded by religion and so it was no surprise that she grew up to become the High Priestess of her local temple, succeeding her mother in that position. She grew up hearing about the good and evil of the world, but never experiencing the world for herself. She never formed her own opinions about the world, so when she heard what the scripture said about demons, she never doubted it. That is, until she met Hades, ruler of The Underworld who'd descended to Mundus in search of an ancient artifact.
Hades was a handsome man, far more handsome than any mortal. Even though he was a demon, there were few Angels who compared to him in terms of beauty or even dare I say moral compass.
It was a nice Saturday afternoon, Phoebe had just finished her daily prayer and was about to head to the market when she found a rather peculiar man. Handsome beyond belief but as clumsy as a child. He looked at everything with such interest, it was as though he'd never seen the outside world before.
-Excuse me, Sir. Do you perhaps need help? I saw you from across the street and you looked as though you were looking for something.
-Fili hominis ecce ego infernum demergeris. Demons ordinatorisque rex ad inferos. Descendi mundus igne conlucere quaerebat antiquam potens artificium.
-Could it be that you're not from around here?
-*totalitarian* I am sorry for that. My translation magic wasn't working properly this time around. You mortals use such a guttural tongue. Anyways, as I was saying, I am Hades, and I came to Mundus in search of the Fiery Gleam, an ancient and powerful artifact.
Afterwards they talked for hours on end. Phoebe was someone who had never left her hometown so hearing stories from someone like Hades was a blessing for her.
5 years later. The Underworld
-My dear Phoebe, our daughter has finally come into this world. What shall we name her?
-Her name shall be Kiera, meaning dark in the mortal tongue. It's an homage to her dark eyes.
Hades turns to his newborn daughter and kisses her forehead. Then an explosion is heard throughout the entire castle. Among all the panic, a knight donning golden armor comes into the room.
-My liege, Arch Demon Asmodeous is attacking the castle. This time his army is several times larger than ours. And he has with him several mages capable of casting the high level spell "Inferno". I'm afraid we'll lose this time.
-No, we won't. *Dlrow siht ot eeht nommus I aer*
An enormous purple light fills the room.
-So, you call on me again, in your time of need Hades. What is it?
-Rea, protect my daughter, Kiera. She's only half-demon, even though she has a golden god-vein. She can't protect herself when she's just a newborn. Form a contract with her, become her spirit partner and nurture her while growing up. I'll send you both to the mortal plane, i'll come to you when it's safe.
And so, a portal to mundus is opened, between cries from Phoebe and laments from Hades. Rea carries the newborn Kiera to Mundus. After they pass through the portal, Hades sheds a tear when he explodes the link connecting the Underworld and Mundus. He knew it was the only way to truly keep his daughter safe. The link wouldn't be gone forever, it'd take time, but he knew it wasn't the last time he'd see his daughter.