Peter Hale is a dangerous and powerful werewolf, and the original alpha who turned Scott McCall into a werewolf years ago. Clashing with Scott's group for years over power and regaining his former alpha status, he was finally defeated and sealed away within a special supernatural holding cell in Eichen House mental health facility. Years passed, and as his mental state diminished his strength grew.
Eventually escaping and becoming as strong as ever thanks to his time locked away, he begins a new plan to kill Scott and his friends by acquiring three new weapons to fight them with. Who or what these weapons are is unknown, but Peter claims them to be the type of thing "You'll never be able to fight against."