Sometimes described as taking the form of a crocodile, giant beaver or dwarf, it is also said to be a demonic creature. The afanc was said to attack and devour anyone who entered its waters.
Various versions of the tale are known to have existed. Iolo Morganwg, who revived Welsh bardic traditions during the 18th and 19th centuries, popularised a version of the myth that had Hu Gadarn’s two long-horned oxen drag the afanc from the lake, enabling it to be killed. An earlier variation on this had the oxen cast the afanc into Llyn Ffynnon Las (lake of the blue fountain), where it was unable to breach its rocky banks to escape.
In one telling the wild thrashings of the afanc caused flooding which drowned all the people of Britain, save two, Dwyfan and Dwyfach. Another has a maiden who tamed the afanc by letting it sleep in her lap, which allowed her fellow villagers to capture it. When the afanc awoke its struggles crushed the maiden.
Later legends had King Arthur or Peredur slaying the monster. Near Llyn Barfog is a rock with a hoof print carved into it, along with the words Carn March Arthur (stone of Arthur’s horse), supposedly made when his steed, Llamrai, dragged the afanc from the deep.
The afanc has been variously known as the addanc, adanc, addane, avanc, abhac and abac. Several sites lay claim to its domain, among them Llyn Llion, Llyn Barfog ad Llyn-yr-Afanc (the Afanc Pool), a lake in Betws-y-Coed.
Source: Dwyfan and Dwyfach – Wikipedia
Tim B.
https://en.wikipedia.org/wiki/Afanc
“Peredur continues to the cave on his own, wishing to kill the creature to increase his fame and honour. On his journey he meets a maiden who states that the Addanc will slay Peredur through cunning, as the beast is invisible and kills his victims with poison darts. The maiden, actually the Queen of Constantinople, gives Peredur an adder stone that will make the creature visible.
Peredur ventures into the cave and with the aid of the stone, pierces the Addanc before beheading it. When the three chieftains arrive at the cave they state that it was predicted that Peredur would kill the Addanc.[1]
Some legends ascribe the creature’s death to King Arthur. Close to Llyn Barfog in Snowdonia is a hoof-print petrosomatoglyph etched deep into the rock Carn March Arthur “Stone of Arthur’s Horse”, which was supposedly made by King Arthur’s mount, Llamrei, when it was hauling the addanc from the lake. “