Prior to the storyline, Ylva was an ally of the creatures in Silverhöjd forest. After Johan Thörnblad sprayed an illegal toxic chemical and unintentionally caused a genocide among the forest creatures, Ylva witnessed the workers burning the bodies. Horrified, she ventured into the forest for any remaining survivors. Fortunately, she found a baby huldrekarl. While the workers searched, Ylva hid and took the baby to her home, naming him Muns.
Years later, her adopted son would lure unsuspecting children into a cave in Silverhöjd Forest to avenge his own kind.