Brân wades across the Irish Sea to rescue her with his brother Manawydan and a huge host of warriors, mustered from the 154 cantrefi of Britain, following in ships.
The Irish offer to make peace, and build a house big enough to entertain Brân, but they hang a hundred bags inside, supposedly containing flour but actually containing armed warriors.
Only seven men survive the conflict, among them Manawydan, Taliesin and Pryderi fab Pwyll, prince of Dyfed, Branwen having herself died of a broken heart.
As instructed, they take the now silent head to the Gwynfryn, the "White Hill" (thought to be the location where the Tower of London now stands), where they bury it facing France so as to ward off invasion.
Soon the boat men came to shore declaring the fleet belonged to the Irish Lord Matholwch who came seeking Bran's sister Branwen's hand in marriage.
Soon after all the wedding and celebration took place Bran's half brother Efnysien returned to Wales and was puzzled to see so many foreign horses stabled.
In his anger he maimed all the Irish horses by cutting their lips back to their gums, their ears down to their skulls, eyelids to eyeballs, and their tails to their rumps.
Bran could not stand for that, so he offered Matholwch a magic black cauldron that could bring the dead back to life on the condition they could not speak.
Matholwch's men seeing the Welsh advance successfully, said they would atone for the injustice done to Branwen by ensuring the kingship of Bran's nephew Gwern.
The house the Irish built however was a clever trick as they hid one hundred soldiers inside bags throughout the home instructed to jump out at the feast and kill the nearest Welshman.
During the great fight Bran took a fatal blow to the foot, and as he lay in his deathbed he gave his men these last instructions: “Cut my head off and take it to London.
[6] There have been attempts in modern times to link the still-current practice of keeping ravens at the Tower of London under the care of Yeomen Warder Ravenmaster with this story of Brân.
Several scholars have noted similarities between Brân the Blessed and the Arthurian character the Fisher King, the keeper of the Holy Grail.
A later author who took up the story, Robert de Boron, describes the history of the Grail in ancient times, and says the first Fisher King was a man called "Bron".
[7] John T. Koch proposes a number of parallels between the mythological Bendigeidfran and the historical Celtic chieftain Brennus, who invaded the Balkans in the 3rd century BC.
[9] Brân is praised in the poetry of 12th century bard Cynddelw Brydydd Mawr, in which he is described as "a good commander of the host; in battle, in hostile territory, in the contest, in stress", while, in his elegy for Llywelyn ap Gruffudd, Prince of Wales, Bleddyn Fardd compares the overthrow of the prince to the deaths of Llywelyn Fawr, King Arthur and Brân.
[10] A poem found in the Black Book of Carmarthen refers to Bendigeidfran's death in Ireland, claiming that Gwyn ap Nudd was present at the battle, either as a warrior or in his traditional role as a psychopomp.
[11] The novel series The Chronicles of Prydain by Lloyd Alexander, whose second installment is named The Black Cauldron, is based on Welsh mythology.
The novel series A Song of Ice and Fire by George R. R. Martin includes several characters named Brandon (Bran) Stark.
In the Mabinogion, the character is referred to virtually exclusively as "Bendigeituran"; that is, with the epithet "Bendigeit" (blessed or praiseworthy) attached (a terminal D is pronounced similarly to T in Welsh, and in early documents was also spelt with T).
[13] "Vran" appears in an old poem in the Book of Taliesin,[14] while Cynddelw Brydydd Mawr and Prydydd y Moch mention Brân fab Llŷr several times in their poetry, under different spellings.
However, Bleddyn Fardd refers to "Benigeitran" in his elegy for Llywelyn ap Gruffudd, demonstrating that the epithet "Bendigeit" had been attached to Brân since the late 13th century.