When Taran, Eilonwy, Fflewddur Fflam, and Gurgi fall in the cave elves and lose consciousness, four fairy children arrive carefully and hide to observe closely. One notes that Doli, whom he calls "Old Doli", improperly repaired the vortex. One of them, a mischievous elf, who is the only girl in the quartet, suggests to tell it to King Eidilleg. But the elf who spoke before her reminds her they are not supposed to be up in places and she receives the wrath of his fellows. Shameful and confused, the little fair folk announces they are all going to be in trouble but the other kids say it will not happen and disappear. The small fair folk decides of escape the problems differently but disappears in turn when she sees King Eidilleg and Doli bustling with the whirpool.
The other folk fair watch silently as Doli gets at it and comes across Hen Wen. The kids, then the adults come out of hiding or leave their home. Doli gets mad to the idea of having to perform another task and gestures; he hosts his hat angrily, give a look up in it and rocking against his, what entertains fair folk children. Even more furious, Doli asks them what they do. The small elf hussy makes a plea, defending and explaining that she just wants to see the pretty girl. This justification does not change Doli's mood who casts out viciously. Obedient, she joins all other fair folk who surround Taran, Eilonwy (surprised and amazed), Fflewddur Fflam (scared) and Gurgi (suspicious). As a fair folk examines Gurgi, this one is captured in his hand and he believes to have trapped her, but the fair folk disappears and reappears next to him, at his astonishment. The folk fair disappear when Hen Wen comes running.
After it was agreed that Doli will guide Taran and his friends in the Morva Marsh, the fair folk bring Taran, Eilonwy, Fflewddur Fflam to the surface. The fair folk are not seen in the rest of the film, except for Doli.
Among the fair folk who surround Taram and his friends, we can see Tinker Bell.
The names of Fair Folk are unknown, except King Eidilleg and Doli who have to protect the cave. No words means one of them. Only the hussy small elf girl is treated of "silly'.
In the books in Lloyd Alexander's fantasy series The Chronicles of Prydain, there are two other fair folk: Glew and Gwystyl. Glew is not a true elf but is small and enters the cave elves and he is discovered by accident when the companions fall into and are trapped in an underground cavern, the Isle Mona.
Gwystyl is one of the Fair Folk, (possibly a sidh) and is described as resembling "a bundle of sticks with cobwebs floating at the top."He appears sickly, with sparse, long and stringy hair. He wears a mournful expression and with his anxious eyes, seems constantly on the verge of tears. His personality is no cheerier; he constantly complains and snivels, is a pessimist and appears cowardly. He avoids conflict by asserting, "I am not up to it today...I'm not well, not at all well, really." Gwystyl lives in a hidden underground waypost near the border of Annuvin, the dominion of the villain of the series. He has a pet crow, named Kaw.
Glew and Gwystyl do not appear in the film The Black Cauldron or else are part of Folk Fair. They can be seen too in the art gallery in the 25th Anniversary Edition DVD of The Black Cauldron.
Gwystyl does, however, make an appearance in the 1986 Sierra Adventure game based on the film, should Taran succeed in delivering Hen Wen safely to the Secret Glade two screens south and one screen west of Caer Dallben.