Welsh mythology
Welsh mythology consists of both folk traditions developed in Wales, and traditions developed by Britons elsewhere before the end of the first millennium. Like most predominately oral societies found in Pre-Roman Great Britain, Welsh mythology and history was recorded orally by Druids (derwydd). This oral record has been lost or altered as result of outside contact and invasion over the years. Much of this altered mythology and history are preserved in medieval Welsh manuscripts which include the Red Book of Hergest, the White Book of Rhydderch, the Book of Aneirin, and the Book of Taliesin. Other works connected to Welsh mythology include the 9th century Latin historical compilation Historia Britonum (the History of the Britons) and Geoffrey of Monmouth's 12th-century Latin chronicle Historia Regum Britanniae (the History of the Kings of Britain), as well as later folklore, such as The Welsh Fairy Book by W. Jenkyn Thomas [1908].
Legends
Four Branches of the Mabinogi
Most mythological stories contained in the Mabinogion collection are collectively titled The Four Branches of the Mabinogi, which concentrate largely on the exploits of various British deities who have been Christianised into kings and heroes. The only character to appear in every branch is Pryderi fab Pwyll, the king of Dyfed, who is born in the first Branch, is killed in the fourth, and is probably a reflex of the Celtic god Maponos. The only other recurring characters are Pryderi's mother Rhiannon, associated with the peaceful British prince Manawydan, who later becomes her second husband. Manawyadan and his siblings Bendigeidfran, Branwen and Efnysien are the key players of the second branch, while the fourth branch concerns itself with the exploits of the family of Dôn, which includes the wizard Gwydion, his nephew Lleu and his sister Arianrhod.