Gmork's primary mission is kill Atreyu the warrior, who intends to stop the Nothing from destroying Fantastica.
He sees Atreyu running off, but isn't able to catch up to him; Atreyu escapes the Mountains of Death using Ygramul's poison.
When Atreyu does meet Gmork, he is chained up by Gaya, Princess of Darkness (reminiscent to Nordic mythology), who wanted to stop Gmork from helping The Nothing to succeed in destroying Fantasica. Gaya was the only one who could free Gmork from the chains, but committed suicide by jumping into the Nothing. Gmork tells Atreyu that if a Fantasican jumps into the Nothing, they will come to the human world and become a lie, giving power to control humans.
As he dies, Gmork unknowingly bites Atreyu's foot, ironically preventing him from jumping into the Nothing. Atreyu is saved by Falkor.
The NeverEnding Story (1984)
In the first movie, Gmork is voiced by Alan Oppenheimer, who also voices Falkor and Rockbiter.
G'mork almost succeeds in killing Atreyu in the Swamps of Despair, but Atreyu is saved by Falkor.
When Atreyu comes across Gmork, he is not in chains, and does not mention the Manipulators. He tells Atreyu that the Nothing would remain once Fantasia was destroyed, because people stop believing in it.
When Atreyu asks who Gmork is, he explains that he was sent to kill a warrior named Atreyu. Grabbing a stone knife, Atreyu reveals himself, and Gmork lunges at him, but Atreyu stabs him with the knife, killing him.
G'mork is tied up to a chain which could be a reference to Fenrir from Norse Mythology, the wolf son of Loki who was chained because the gods feared him.