Afanc

Medieval attestations place the creature in Welsh narrative cycles and manuscripts: the Addanc appears in the Peredur tale (White Book/Red Book tradition) as a lake/cave-dweller overcome by a hero, and poets such as Lewys Glyn Cothi (15th c.) mention an afanc living in Llyn Syfaddon. In manuscript tradition the name appears in variant forms (Middle Welsh avanc, Modern Welsh afanc, and addanc in some versions), showing long transmission. Later antiquarian and local legends, notably accounts associated with the antiquary Iolo Morganwg, recast the afanc as an agent of catastrophic flooding (its thrashings drown the inhabitants of Britain save two survivors) and relate tales in which Hu Gadarn’s oxen drag the creature from its lake so it can be killed; these later narratives link the afanc to etiologies of place‑names and floods.

Descriptions vary across sources and time. Medieval narratives do not fix a consistent morphology: the Peredur Addanc is functionally described (invisible and killing at range with poison darts) rather than given a precise corporeal form. Other strands and later popularizations portray it in diverse ways—beaver-like in some linguistic developments of the name, crocodile-like in popular retellings, or as dwarf-like in some accounts. Modern fictional descriptions (not medieval attestations) have sometimes depicted it as a marsh creature the size of a cow with fur, scales and many teeth. The tradition therefore preserves a stable role (lake-monster) while allowing variation in outward appearance.

Across sources the afanc is presented primarily as a predatory lake-being that kills those who enter or fall into its waters. In the Peredur tale the Addanc is specifically described as invisible and slaying victims with 'poison darts'—a capacity tied to that narrative and overcome there by an adder stone that makes the beast visible. In Iolo Morganwg’s account the creature’s violent thrashings are said to have caused massive flooding; in that version the afanc can be dragged from its watery environment (by Hu Gadarn’s oxen) and rendered powerless once removed from the water. Other stories record extraordinary close-contact strength (crushing a woman when it awakes) and recurring lethality (the Addanc slays three chieftains daily in Peredur until they are restored by maidens).