Branwan, Branwen ferch Llyr
Branwen's story is best known from a part of the Mabigioni, which sometimes is called Mabinogi of Branwen. She is the daughter of Llyr and Penarddun, wife of the King of Ireland, Matholwch. She is sister of Brān the Blessed (also known as Bendigeid Vran, who is the king of Britain, and half-sister of Efnisien.
Bendigeidfran sits at Harlech on a rock by the sea, seeing the ships of Matholwch coming. The Irish king has come to ask for Branwen's hand in marriage, which Bendigeidfran agrees to. When the feast is held in their honor, to celebrate the betrothal, Efnisien, arrives and asks about the celebrations. He gets furious when he hears of the marriage and he hadn't been asked. Because of this he mutilates Matholwch's horses. The king is deeply offended by this act and Bendigeidfran gives him a magical cauldron which can bring the dead back to life, the downside is that they then are mute.
Matholwch treats his wife cruelly - as a punishment for his horses - but she gives him an heir, named Gwern. In desperation she tames a starling, sends it to her brother with a message, across the Irish Sea. When Bendigeidfran reads this he summons his forces and goes from Wales to Ireland to rescue her. Some swineherds saw the giant Bendigeidfran wading the sea and brings this news to their king, Matholwch, who retreats beyond a river and destroys all the bridges in an attempt to stop his brother-in-law.
Bendigeidfran lays himself down over the river, letting his men pass the river over him, uttering the gnomic words:
'A fo ben, bid bont'
'He would be a leader, let him be a bridge.'
In fear Matholwch builds a house big enough to house the giant, to do him honour, and agrees to give the kingdom to his son, Gwern, to oblige Bendigeidfran. The Irish lords didn't like this and hid themselves in flour bags in the building to attack the Welsh, but they are killed by Efnisien who squeezes their heads. During the feast to celebrate Gwern his uncle, Efnisien, in an unprovoked moment of rage throws Gwern into the fire.
The ensuing war was a bloody one - all the Irish are killed, save for five pregnant women in Wales who repopulate the island. Only seven of the Welsh warriors returned home with Branwen, as well as the severed head of Bendigeidfran. When they arrived in Wales as Aber Alaw in Anglesey, Branwen dies of grief because of all the destruction and is buried by the river Alaw.
'Oi, a fab Duw! Gwae fi o'm genedigaeth. Da o ddwy ynys a ddiffeithwyd o'm hachos i!'
'Oh Son of God, woe to me that I was born! Two fair islands have been laid waste because of me!'
Her brother Bendigeidfran had given the order to his man to cut off his head and to
bear it even unto the White Mount, in London, and bury it there, with the face towards France.
His men spent seven years in Harlech, feasting accompanied by three singing birds and Bendigeidfran's head. After those seven years they went to Gwales in Penfro, where they stayed for fourscore (80!) years. In time they went to London and buried the head of their leader in the White Mount. The legend says that as long as the head was there, no invasion would come over the sea to Britain.
There is a cairn called Bedd Branwen on the banks of the Alaw river, at Llanddeusant in Anglesey. It is in ruins, but it still has one standing stone. In 1800 it was dug up, and again in the 1960s by Frances Lynch, who found several urns with human ashes. If the story is true it should have been taken place during the British Bronze Age period.