G'mork as portrayed in the first film.
G'mork is a character in Michael Ende's novel The Neverending Story.
Novel
In the book, Gmork's knowledge of Fantastica is taught to him by the The Manipulators, the power behind The Nothing.
Gmork's primary mission is kill Atreyu the warrior, who intends to stop from destroying Fantastica.
He sees Atreyu running off, but isn't able to catch up to him; Atreyu escapes in Swamps of Sadness using Ygramul 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 commited suicide by jumping into the Nothing. Gmork tells Atreyu that if a Fantasican jumped into the Nothing, they would come to the human world and become a lie, giving power to control humans.
As he dies, Gmork unknowningly bites Atreyu's foot, ironically preventing him from jumping into the Nothing; Atreyu is saved by Fuchur.
Films
The NeverEnding Story (1984)
In the first movie, Gmork is voiced by Alan Oppenheimer.
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.