TW: mentions of infant death, child abuse, and parentification ahead!
Sarah Rose Abadeer is the middle child of Hunson Abadeer, a demon lord of a hell-like dimension known as the Nightosphere, and Elise, a human woman. While Elise was able to carry Sarah to term, Sarah came out as a stillborn. Distraught, Hunson struck up a deal with Death to get her soul and used dark magic to bring her to life. It worked and from that point on, Hunson began to raise Sarah by himself, leaving Elise unaware of Sarah’s existence.
Sarah grew up being raised by Hunson alongside her younger siblings, Marsha and Damian. Just like her younger siblings, Sarah’s childhood was a lonely one. For as far back as she could remember, Sarah was made to look after her younger siblings. While Sarah never resented them, this way of life made her grow up a little too quickly. Aside from her younger siblings, Sarah didn't have any friends and was often tormented by her younger cousin, Heather, who would often manipulate the adults in order to get Sarah into trouble. So Sarah would come to prefer spending time with her younger siblings.
And just like the twins, she was often subjected to Hunson’s wrath. Outside of being made to look after the twins, Hunson and Sarah wouldn't have that much of a relationship outside of that mostly due to Hunson heavily focusing on the twins. Despite this, Sarah was similar to them in wanting to be close to her father.
What made it even worse was when Hunson began to train Marsha to join the family business. While he was initially training them both, he mostly came to focus on Marsha when she was better at magic than Sarah was. Despite this treatment, Sarah and her siblings still remained on good terms and close. This level of closeness still remained true, even when it was tested in during their early teen years when Marsha slowly began to push away from Sarah, blaming herself for what Sarah had to go through during their childhood.
Shortly after the fight that resulted in the loss of Marsha’s soul, Marsha managed to convince Damian and Sarah to run away with her, not wanting to leave her behind. Sarah agrees, which resulted in them struggling to survive in the wastelands of the surface world where they both did things that they’re not proud of. They wander around for hundreds of years until they come across a cottage that they make their home.