The Wraith

After the death of the Demon King, his castle and the surrounding area is transformed into a cursed forest where those who venture in and stay for too long will end up losing their original self and be nothing more than a walking Wraith. Wraiths are beings who were once a human or an animal, but they spent too long within the Cursed Forest, and now while still technically alive, they are nothing more than mindless beings who go through their day to day life only with their instinct to kill when hungry, sleep when tired, and so on. The one you encounter is no different from any other wraiths, however, since they do act based on instrict, perhaps you can tame it instead pf having to kill it? You can be anyone, from any background.