The return of Bendigeidfrân head idea

Branwen, Daughter of Llŷr

In the second branch, Branwen, sister of Bendigeidfrân (meaning Bran the Blessed), king of Britain, is given in marriage to Matholwch, king of Ireland. Branwen's half-brother Efnisien, angry that he was not consulted, insults Matholwch by mutilating his horses but Bendigeidfrân gives him compensation in the form of new horses and treasure, including a magical cauldron which can restore the dead to life. After returning to Ireland Matholwch and Branwen have a son, Gwern, but Efnisien's insult continues to rankle among the Irish and Branwen is banished to the kitchen and beaten every day. Branwen trains a starling to take a message to Bendigeidfrân, who goes to war against Matholwch. His army crosses the Irish Sea in ships, but Bendigeidfrân is so huge he wades across. The Irish offer to make peace and build a house big enough to entertain Bendigeidfrân but hang a hundred bags inside, supposedly containing flour but actually containing armed warriors. Efnisien, suspecting a trick, reconnoitres the hall and kills the warriors by crushing their heads inside the bags. Later, at the feast, Efnisien, again feeling insulted, throws Gwern on the fire and fighting breaks out. Seeing that the Irish are using the cauldron to revive their dead, Efnisien hides among the corpses and destroys the cauldron, although the effort costs him his life. Only seven men, all Welsh, survive the battle, including Pryderi, Manawydan and Bendigeidfrân, who is mortally wounded by a poisoned spear.

Bendigeidfrân asks his companions to cut off his head and take it back to Britain where it continues to live for sometime as they partake of an enchanted feast. Branwen dies of grief on returning home. Five pregnant women survive to repopulate Ireland.