In the movie, Gmork is not in chains and says no word about the manipulators, but tells Atreyu that the Nothing would be the emptiness that would remain because people stop to believe into phantasy. He tells the boy that he has to kill someone named Atreyu and when he reveals that he's Atreyu, Gmork attacks him.The werewolf gets impaled by a knife in Atreyu's hand.
In the book, Gmork's knowledge of Fantasia is taught to him by the the Manipulators, the power behind the Nothing. His primary mission was to kill Atreyu, however he never does it: he never catches up Atreyu that escapes in the Swamps of Sadness using Ygramul poison. He only meets him after he's taken in chains by Gaya, princess of darkness, (reminiscent to Nordic mithology) who wanted to keep Gmork from helping the Nothing to succeed. Gmork tells Atreyu that she was the only one able to free him, but she commited suicide by jumping into the Nothing. He further tells him that if a being of Fantasia would jump into the Nothing, it would travel to the human world, becoming a lie. And the lies would give power to control humans. Gmork dies, but his body bites Atreyu's foot and ironically keeps him from jumping into the Nothing. However, Atreyu was saved by Fuchur.