Lleu Llaw Gyffes — 'the fair-haired one with the skilful hand' — is the radiant, sun-touched hero of the Fourth Branch of the Mabinogi, and one of the central figures of Welsh myth. Born of the maiden Arianrhod and raised by his uncle, the magician Gwydion, Lleu lived under three curses his angry mother laid on him: that he would have no name, bear no arms, and take no wife of any race now on the earth — each of which Gwydion overcame by trickery or magic, winning Lleu his name and his weapons, and conjuring for him a bride out of the blossoms of oak, broom and meadowsweet, the flower-woman Blodeuwedd.
The story
But Blodeuwedd betrayed him. Falling in love with the hunter Gronw Pebr, she coaxed from Lleu the strange and single way in which he could be killed — neither indoors nor out, neither on horseback nor on foot, by a spear a year in the making and worked only during Mass on Sundays — and arranged for Gronw to strike him so, as Lleu stood with one foot on a cauldron and one on a goat by the riverbank. At the blow Lleu gave a terrible scream and rose into the air as an eagle, vanishing into the sky.
Gwydion searched all Wales for him and at last followed a sow to an oak tree at Nantlle, where the eagle perched, rotting and wasted, with maggots falling from its flesh. Singing magical verses, Gwydion coaxed the bird down onto his knee, struck it with his wand, and restored Lleu to human form. Lleu was nursed back to health, took his revenge on Gronw — who was killed by a spear through a standing stone — and Blodeuwedd was turned by Gwydion into an owl, condemned to haunt the night. Lleu lived on, in time to become lord of Gwynedd; tradition places his hall at Mur Castell, the site of Tomen y Mur near Trawsfynydd.