[1] The Afanc, a monster that lived in Llyn Llion (which could be Bala Lake) caused a huge flood.
[1] A lake monster from Welsh mythology, the afanc can also be traced through references in British and Celtic folklore.
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.