Afanc (avanc). There was some doubt about the form taken by the monster which inhabited a pool called Llyn yr Afanc on the River Conwy in North Wales. It was generally thought to be an enormous beaver because the word afanc is sometimes used for beaver in local dialects.
Llyn yr Afanc is a kind of whirlpool: anything thrown into it will whirl round about before it is sucked down. It used to be thought that it was the Afanc which dragged down animals or people who fell into the Llyn. It was
thought to be either a monstrous beaver or a kind of crocodile.
According to a 17th-century tradition told in Rhys’s Celtic Folklore (p. 130), the Afanc, like the Unicorn, was allured by a maiden who persuaded it to lay its head in her lap and fall asleep. While it slept it was chained and the chains were attached to two oxen. When they began to draw it, it awoke and made for the pool, tearing away the maiden’s breast which it was holding in its claw. Several men hauled on the chain, but it was the oxen’s strength that was effectual, as the Afanc itself confessed. The men were disputing as to which of them had pulled the hardest when the captive suddenly spoke and said
Had it not been for the oxen pulling,
The Afanc had never left the pool.’
SOURCE:
An Encyclopedia of Fairies: Hobgoblins, Brownies, Bogies, and Other Supernatural Creatures written by Katharine Mary Briggs – Copyright © 1976 by Katharine Briggs