- “Show us where the Black Cauldron can be found! [...] Go on! Show us, swine! I warn you, the King's patience is short!”
- ―Creeper interrogating Hen Wen
Creeper is intelligent and fiendish, and is loyal to the Horned King, but is also afraid of him due to his mistreatment towards him. The Horned King blames Creeper for things and chokes him when he thinks he isn't doing what he wants him to do. Although Creeper enjoyed nothing more than serving the Horned King, he hated his master (Mainly due to being so terrified of him), as evidenced by his joy at the Horned King's death. Also, in spite of being the King's second-in-command, he receives little to no respect from his soldiers, as during times he is not giving them orders, he is constantly abused and pushed around by them, (similar to his master's treatment of him but on a lesser scale) which is shown during their celebration in their successful capture of Hen Wen, Taran's pet pig.
Creeper is a small goblin with green skin and a right eye that is sometimes closed. He wears a purple cowl and brown skirt.
Creeper appears during the celebration of the capture of Taran's pig, Hen Wen; here it is shown that Creeper is often the target of his soldiers' bullying rather than their superior (being the Horned King's first officer). Afterward, Creeper is ordered to force Hen Wen to show him the Black Cauldron, though she resists until he threatens her with fire. Creeper succeeds, with the help of henchmen. Taran, afraid, pours the liquid of the revelation of the Black Cauldron into the Horned King eye. Taran runs and Creeper, the Gwythaints, and the human henchmen chase him. The Horned King finds that the pig is gone, so he briefly strangles Creeper out of spite before ordering the human henchmen to throw Taran into the dungeon. Creeper orders a henchman to moves along with a lifeless skeleton in a rolling basket. Creeper and the henchman find Taran, and his new friends: Princess Eilownly and Fleudder Flam are missing, so Creeper and the human henchman chase them, but the captives escape. The Horned King is apparently angry when Creeper fearfully reports to him that Taran had escaped, but the farmer knows that the boy will eventually find Hen Wen and orders Creeper to sends the Gwyithaints to follow Taran, much to Creeper's relief and delight.
Creeper appears again after the human henchmen capture Taran, Princess Eilownly, and Fleudder Flam once more. Creeper orders a human henchman to take the dead skeleton to and park at slightly near the Black Cauldron. Creeper taunts the captives and he and human henchmen watch the Horned King bring the skeletons to life, and the henchmen (except Creeper and the Gwyithaints) run away in fear. Creeper and the Horned King celebrate with glee. Gurgi jumps into the Cauldron (he is revealed to be alive at the end) to stop the life of the skeletons after he frees the captives. Creeper and the Horned are shocked that the skeletons are now dying. The Horned King suspects Creeper is the one to blame. Creeper suggests that they are only resting as the Horned King shouts, "Get UP, you fools! KILL!".
Creeper sees Taran and says it is him who is to blame and laughs with glee as the king prepares to kill Taran. However, the cauldron is angry for its powers being sucked up and drags the Horned King to itself. Despite the fact that the Horned King attempted to pull himself out, he is sucked into the cauldron. Creeper is sad for a short moment but realizes his master is gone and unable to punish him whether it is his fault or not. Laughing, he leaves and manages to save a Gwythaint from dying in the burning of the castle and escapes riding on it, mockingly wearing the horns of his fallen master and cackling.
Creeper doesn't appear on the show. However, a Gnome who appeared in "The Thing You Love Most" as the Evil Queen's ally before she instantly turns him into a stone statue, has a similar characteristic and behavior.
Vomit, a goblin who appears in the sixth episode "Stonehenge Your Bets" has a design that is very similar to Creeper.
- Creeper is original to the film and was never a part of the Chronicles of Prydain book series.
- Creeper is very similar to Fidget from the film The Great Mouse Detective, and to "Toadie" Toadwart from Adventures of the Gummi Bears.
- In the book, Creeper is also Achren the one who's with Arawn's army.
- For the Italian version of the film, Creeper's name, likely deemed too much English-sounding, was changed to "Rospus", a Latin-sounding word deriving from the Italian "rospo", "toad".