On-set, the production used the term Void Stiles to differentiate between the primary, "good" character and the "evil", Nogitsune-possessed version of Stiles as each had different make-up, costuming and lighting effects. Fans soon picked up the term and spread it through social media.
After "dying" during a symbolic sacrifice to save his father, Stiles' soul is left vulnerable to influence by an ancient Japanese spirit. He is possessed by the Nogitsune and wreaks havoc on his friends.
Thanks to an intervention by Scott McCall and Lydia Martin, Stiles is able to escape the void spirit's grasp. They separate into two distinct beings, Void Stiles and Stiles. The original is left severely weakened as a result.
Stiles returns to normal after Scott destroys Void Stiles with a bite.
Main Article: Stiles Stilinski (Season 3)