Serina lived in the forest as a warden, hunting down and chasing away spirits from the forest around the walls of Thach. Her favorite part of the job had always been tending to and training the wolves that could sniff out the evil creatures. The wolves would lead her and the other wardens to the dens, and the wardens would drive the spirits out by carving magic sigils into bark or by slaying possessed animals. Those wolves became more than mere tools to Serina; they became her best friends and preferred company. One great white wolf, the first she trained, had been with her for everything, and she loved him greatly.
One night when Serina was alone at camp, an old man dressed in leaves and twigs approached her. He offered to make her closer to her wolf and able to understand his kind for the price of some of her humanity. She thought he meant only her soul, and as soon as she agreed, the camp was swallowed by darkness. Serina was filled with agony for only a moment before blacking out.
The others returned to find an odd body laying face-down in the dirt. Its shape was human, and white fur covered what showed of her arms and legs, which ended in paws rather than feet. A long, thick tail sprouted from beneath her torn shirt, and pointed ears grew from the top of her head. One warden hesitantly approached, but as he bent down to see what it was, the monster leapt up and fled fast, hiding its face from the humans.
When Serena traded away her humanity, her pet's spirit filled the vacuum left in her. She became able to communicate with wolves through her thoughts and theirs, seeing the things they had seen in her mind's eye, but at the cost of her human beauty.
Serina also finds herself frequently tormented by inhuman desires, and while she learned quickly how to suppress the violent urges, the need to mate often blanks her human thoughts out, and she finds it incredibly difficult to turn down almost anything that wants her. Worse yet, sometimes she'll fall into a heat, and lose days of memory where she did almost nothing but hunt down things to fuck. She spends her days of consciousness seeking revenge on the spirits and looking for someone who will accept her and protect her from herself. The other days, she doesn't care to think about.