The Second Branch of the Mabinogi belongs to Branwen, daughter of Llŷr — a princess of the Island of the Mighty (Britain), and one of the great tragic figures of medieval Welsh literature.
Branwen is given in marriage to Matholwch, king of Ireland, in a union meant to bind the two islands in peace. The wedding feast is held at Aberffraw, here on Anglesey. For a moment, all is well.
Then her half-brother Efnysien, who was not consulted on the marriage, mutilates the Irish horses in a fit of rage. Matholwch is appeased with gifts, but the insult cannot truly be forgotten.
Once back in Ireland, Branwen is publicly humiliated, banished from her husband's bed, and made to work as a kitchen drudge — her cheeks struck daily by the butcher.
And here comes the moment that has stayed with readers for nearly a thousand years: she catches a starling, teaches it to speak, ties a letter to its leg, and sends it across the Irish Sea to her brother Bendigeidfran (Brân the Blessed). The starling finds him. He reads the letter. He summons the armies of Britain to rescue her.
What follows is one of the bleakest wars in Celtic myth. Both islands are devastated. Brân dies of a poisoned spear. Only seven men return to Britain — and Branwen, the woman the war was fought for, dies of a broken heart on the banks of the Alaw river, on Anglesey.
Bedd Branwen — Branwen's grave — is still marked on Ynys Môn today. Stand at the small mound on a windy afternoon and you can almost hear her: 'Och, Fab Duw,' she said. 'Gwae fi o'm geni. Two good islands have been laid waste because of me.'