Gwern

Gwern; "Alder," is a minor figure in Welsh tradition, the son of Matholwch king of Ireland, and Branwen, sister to the king of Britain. He appears in the tale of Branwen, daughter of Llŷr, in which he is murdered by his sadistic uncle Efnysien which sparks a mutually destructive battle between Britain and Ireland.

Matholwch, King of Ireland, sails across the Irish Sea to ask the British High King, Brân, for the hand of his sister Branwen in marriage. Bendigeidfran agrees to this, but during a feast to celebrate the betrothal, Efnisien, a half-brother of Branwen and Bendigeidfran, arrives and asks what was going on. When told, he is furious that Branwen has been given in marriage without his permission, and retaliates by mutilating Matholwch's horses. Matholwch is deeply angered until Bendigeidfran gives him a magic cauldron which restores the dead to life.

Once in Ireland, Branwen is treated cruelly by her husband, Matholwch, and is forced to work in the kitchen. She tames a starling and sends it across the Irish Sea with a message to her brother Bendigeidfran, who sails from Wales to Ireland to rescue her with his brother, Manawydan and a host raised from the one hundred and fifty four cantrefs of Britain. The Irish offer to make peace by building a house big enough to entertain Bendigeidfrân but hang a hundred bags inside, supposedly containing flour but actually containing armed warriors. Efnisien, suspecting treachery, reconnoitres the hall and kills the warriors by crushing their skulls.

So as to make peace between the kingdoms, Branwen and Matholwch's young son, Gwern, ascends to the throne of Ireland and, during the feast held in the Great House in his honour, is called in turn to his uncles Bran, Manawydan and Nisien. He is then called to Efnysien who, seemingly without motive, throws the boy into the flames, burning him to death. Branwen attempts to rescue her son from the fire but is held back by Bendigeidfran.

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