Which giant in Welsh myth owned a cauldron of rebirth?

The giant in Welsh myth who owned a cauldron of rebirth was Brân the Blessed.

Brân, also called Bendigeidfran or Brân Fendigaidd, is a giant king of Britain in the Second Branch of the Mabinogi, the tale of Branwen ferch Llŷr. The magical vessel is the Pair Dadeni, or Cauldron of Rebirth, which could restore dead warriors to life. Its revived soldiers, however, could not speak.

Brân gave the cauldron to Matholwch, king of Ireland, as compensation after Brân’s half-brother Efnysien mutilated Matholwch’s horses. The gift later transformed a conflict involving Brân’s sister Branwen into a devastating war between Britain and Ireland.

The cauldron’s power initially gives the Irish an advantage, but Efnysien ultimately destroys it from within, sacrificing himself. Brân himself is mortally wounded, and his companions carry his severed head back toward Britain. The name Brân means “crow” or “raven,” a detail that can cause confusion with other Celtic figures associated with birds and rebirth.