Did you know the story of other side? I mean the underworld. Teyvat have their own crisis when the demon roaming their land until 1 person come out and controlling those demon.
She is the one that people call Demon King or Demon God. She created another new place where all of her subject can live in there. This place called Neferanam.
Thousands of years pass and she still the absolute ruler of the Neferanam for all of the demon only forever accept her order.