The Gwythaints are based on wyverns, with sharp talons, large, leathery wings, antelope-like horns, and gray/black scales.
The Gwythaints are evil and savage, but also very intelligent of tracking down their targets.
The Gwythaints serve as the Horned King's minions and dragons. He sends them on missions to find for whatever he is looking. They manage to find Hen Wen when Taran accidentally lets her escape in the woods. Taran sees the Gwythaints and tries to help hen Wen and fight the Gwythaints. However, one of them hurts Taran with its claws. They capture Hen Wen and take her back to the castle.
They are later seen celebrating the capture of Hen Wen, along with Creeper and the other henchmen. One of the henchmen gives the two Gwythaints a bone to eat, which they do until the Horned King arrives.
Later, when Taran and Hen Wen try to escape, Creeper, the henchmen and even the Gwythaints try (without being ordered) to give chase. The Gwythaints break free of their chains but pull out the bricks attached on the walls, causing them to fall down and forcing the henchmen to give up for a few seconds. Creeper and the henchmen capture Taran but not Hen Wen, who escapes in a moat.
The Gwythaints are later sent to follow Taran to find the Black Cauldron, while they succeed, they are chained up again. One of them is killed when the Horned King's castle is destroyed and the other Gwythaint is saved by Creeper, off-screen. The Gwythaint escapes with Creeper, laughing madly that the Horned King can no longer punish him, riding on his back and flies away.
- The Gwythwaints are designed after a wyvern, a dragon-like creature sporting two wings and two legs, as opposed to four legs and two wings like a typical western dragon, much like a pterosaur.
- Unlike Creeper and most of the other minions, the dragons seem to love and respect the Horned King.
- They have appeared on numerous occasions in House of Mouse.
- They are as rapacious as their master.
- In the original book series by Lloyd Alexander, The Chronicles of Prydain, the Gwythaints are giant bird-like creatures that are in no way reptilian as they are portrayed in the movie.
- The Gwythaints' roars were also used in non-Disney animated films like Don Bluth's The Land Before Time and Richard Rich's The Swan Princess.
- The Gwythaints have a tail spike array (or thagomizer) similar to that of a Stegosaurus, but with the added diamond tail tip seen in traditional dragons and wyverns.
- They bear some resemblance to Maleficent in her dragon form.