The Cynvael River is a recurring landmark in the conflict between Llew Llaw Gyffes and Gronw Pebyr: beside it, a hunt brings Gronw to Blodeuwedd’s court, an ambush is arranged, and the two men later meet to settle their claims. The pierced slab left on its bank gives the river a material reminder of the conflict and its outcome.

Setting and the Hunt

Gronw’s first appearance at the river is as a hunter pursuing a stag. He overtakes and kills it by the Cynvael River, then remains there into the evening while the stag is flayed and his dogs are baited. As night approaches, he reaches Blodeuwedd’s court; she has him invited in rather than let him depart at that hour. Their meeting there begins the affair and conspiracy that will draw the river back into the story as the site of an attack.

The Ambush on the Bank

A year later, after Gronw has finished making the spear, Blodeuwedd arranges for him to lie in ambush on Bryn Kyvergyr, on the bank of the Cynvael River. She also has the cantref’s goats gathered and brought to the opposite side of the river. The arrangement enables her to persuade Llew to demonstrate the unusual position in which he could be wounded: with one foot on the edge of a bath and the other on a buck. As Llew takes that position, Gronw strikes him with the dart. The riverbank thus becomes the setting for a carefully prepared betrayal, not merely the place where the two men first crossed paths.

The Duel and Llech Gronw

After Llew has recovered, Gronw sends messengers offering land, territory, gold, or silver as compensation. Llew refuses those offers and demands that Gronw stand where Llew had stood when he was struck, while Llew takes the attacker’s former position. They meet on the banks of the Cynvael River and exchange places. Gronw asks to put a slab from the riverbank between himself and the blow, appealing to Llew to allow this because a woman’s wiles had led him to commit the deed. Llew agrees. His dart pierces both the slab and Gronw, killing him. The slab remains on the riverbank in Ardudwy, its hole marking the force of the blow; it is known as Llech Gronw.

A Landmark of Conflict and Aftermath

The river’s role is defined by the sequence of events staged along its bank: Gronw’s hunt, the preparation and execution of the ambush, and the exchange that ends in his death. The surviving slab makes that final encounter unusually tangible in the narrative. After Gronw’s death, Llew takes possession of the land again and prospers in its rule, becoming lord over Gwynedd. The Cynvael River therefore marks both the turning point in their struggle and the place from which Llew’s restored authority follows.