According to the “Mysterious Britain and Ireland” website Llyn Morwynion, overlooked by the fine ring cairn upon Y Garnedd:
“...is probably the lake where, according to the Mabinogion, Blodeuedd and her Maidens of Ardudwy drowned whilst fleeing from the wizard Gwydion and the men of Gwynedd.”
mysteriousbritain.co.uk/legends/llyn-morwynion-lake-of-the-maidens/