Lleu Llaw Gyffes was the illegitimate son of Arianrhod. She was ashamed that she lost her virginity that she place 3 curses (tyngedau) on him. The first was that he should not be named. His foster father Gwydion tricked her into naming him. The second was that he would receive arms from no one. Again she was outwitted by her brother Gwydion and tricked into arming Lleu herself. The third was that he would receive no human wife.
Gwydion and Math worked together creating a woman using flowers of the oak, broom and meadowsweet and gave her the name Blodeuwedd (Flower-Faced). She was destined to be Lleu’s wife. However, Blodeuwedd loved another and whilst her husband Lleu is away, she has an affair with Gronw Pebr, who is Lord of Penllyn (near the head of Llyn Tegid, better known as Lake Bala). Blodeuwedd and Gronw plan Lleu’s murder.
Lleu’s scheming wife tricked Lleu into revealing how he may be killed. He tells her that the only way he can be killed is at dusk, only if he is wrapped in a net with one foot on a cauldron and one on a goat. And only with a spear forged for a year. However, foolish Gronw only acts upon part of the information provided by treacherous Blodeuwedd. He struck at spear at Lleu. However, Lleu transformed into an eagle and flew away. Gronw and Blodeuwedd seize Lleu’s land.
His foster father Gwydion tracks Lleu down, discovering him high in an oak tree. Gwydion sang an englyn (a short Welsh and Cornish poem) to lure him down. He uses his magical powers to transform Lleu into human form. Lleu is in poor health, but with nursing care from Gwydion and Math he soon recovers. He mustered a loyal Gwynedd army and reclaimed his land.
Before Blodeuwedd fled, Gwydion transformed her into an owl, and cursed her to be harassed and despised by all other birds. And from that day Blodeuwedd became the name of the owl.
Gronw, however, escaped to Penllyn. He sent emissaries to beg Lleu’s forgiveness. Lleu refused and demanded to face Gronw by the bank of Cynfael River and deliver a blow from his spear. Gronw asks his army if anyone will take his place, but all refuse. Gronw agreed to Lleu’s terms as long as he could place a large stone between himself and Lleu. Lleu agreed, but so powerful is Lleu’s throw that it pierces the stone and kills Gronw.
The stone remains to this day in Ardudwy. Lleu eventually became the next king of Gwynedd.