It was at Mur-y-Castell (the old name for Tomen-y-mur) that Lleu Llaw Gyffes lived with his beautiful wife Blodeuedd. Lleu was the son of Arianrod the niece of Math fab Mathonwy, king of Gwynedd. Arianrod had cursed Lleu for the shame his birth brought upon her, saying that he would never have a name or bear arms unless she gave them to him, and that he would never have a mortal wife. But her brother, the magician Gwydion, deceived her into naming and arming him, and made him a wife of flowers; and Math fab Mathonwy gave them the kingdoms of Ardudwy and Eifionydd, and Mur-y-castell to be their home.
One day when Lleu was visiting Math fab Mathonwy, Gronw Pebyr, lord of Penllyn, came to Mur-y-castell on a hunting expedition. He and Blodeuedd fell in love and conspired to kill Lleu. He could not be killed inside a house or outside a house, on horseback or on foot: but Blodeuedd persuaded him to show her how this was possible. They built him a bath-house in the woods, on the banks of the river Cynfal, and he stood with one foot on the bath and the other on the back of a stag. Then Gronw hit him with a poisoned dart, but Lleu turned into an eagle and flew away. He was rescued and cured by his uncle, and he and Gwydion came back to Mur-y-Castell to avenge themselves on Blodeuedd and Gronw.
Blodeuedd and her maidservants ran away along the line of the Roman road and across the Cynfal to a court in the mountains, but they were afraid to turn their backs on Gwydion and, unable to see where they were going, the maidens fell into Llyn y Morwynion, the Lake of the Maidens, and were drowned. Gwydion would not kill Blodeuedd but turned her into an owl, so that she might never see the day again and all the other birds would attack her: and so it is that in Welsh the owl is called Blodeuwedd, the flower-faced. Gronw’s warriors and foster-brothers all deserted him, and Lleu slew him by throwing a spear at him through a slab of stone.
Follow the line of Sarn Helen north from Tomen-y-mur and you wil reach a farm called Llech Gronw. Here an old farmer showed us a slate slab with a hole in it, standing in a field above the track. The stone is locally known as Llech Gronw, the standing stone of the legend with the hole driven through it by Lleu in his rage and grief.
Further along the line of Sarn Helen is the Iron Age hill-fort of Bryn y Castell, and away to the right over the spur is Llyn y Morwynion, the grave of Blodeuedd’s maidens. Was Bryn y Castell the ‘court’ they were making for and, if so, does this suggest a tradition that it was occupied in the early medieval period? Or did the story develop around a known ancient feature in the landscape?