Gmork is the secondary antagonist of The Never Ending Story.
He is a werewolf and the servant of the power behind The Nothing. His physical appearance is that of a large, wolf-like creature with night-black fur and capable of human speech. The film shows him as having short, dark, blue-black fur and luminous green cat-like eyes, as well as more fangs than an ordinary wolf would have.
Gmork's primary mission in the Neverending Story is to track down and kill the young warrior Atreyu. He, and other dual-natured creatures like him, do not possess a world of their own like Fantasticans and humans do. Instead, he is able to travel between worlds, changing into a Fantastican or a human depending upon the world, but in appearance only. His knowledge of Fantastica interested the Manipulators, which is why they gave him his mission. However, he never manages to catch up with Atreyu, because the latter uses the magical powers of the monster Ygramul's poisonous bite to wish himself to the Southern Oracle.
Atreyu finally meets Gmork in Spook City, where he is chained, and Atreyu employs the name 'Nobody' to hide his identity in shame of his failure to complete his quest. Gmork confesses that he has been hunting a boy sent on a quest by the Childlike Empress to find her a new name, but lost him early on. He then met the Princess of Darkness, Gaya, who upon hearing of his mission to help the Nothing, chained Gmork with an unbreakable magical chain and leapt into the Nothing, leaving him to starve. Gmork explains to Atreyu the nature of the Nothing, and that if a Fantastican enters it, they become a 'lie' in the human world. Eventually, Gmork reveals the name of the boy he is pursuing, and Atreyu reveals his identity, which causes Gmork to laugh until he finally succumbs to starvation.
Gmork's fate, bound with an indestructible chain, is reminiscent of Fenrir in the Nordic mythology.
In the movie, Gmork almost manages to kill Atreyu in the Swamps of Sadness, but Atreyu is saved just in time by Falkor the luckdragon. Their meeting in Spook City occurs in the movie as well; Gmork, however, is not depicted as tied, and does not name "Manipulators" as the power behind the Nothing. He attacks Atreyu, impaling himself on an improvised stone knife held by the young warrior.
In the book, Gmork's evil lives on after his death. As Atreyu approaches the dead wolf, the carcass lashes out and grabs Atreyu in its jaws. Being held by Gmork, however, prevents Atreyu from being able to give in to the overpowering urge exerted by the Nothing to throw himself into it. He is freed from Gmork's grip by Falkor, who escapes with him to the Ivory Tower.
In Tales of the Neverending Story, Gmork is a werewolf-type creature under Xayide who invades Bastian's world to assume the guise of Mr. Blank to keep an eye on him and stop his meddling.