Arthur, the focus of an extensive medieval cycle of legends and romances, was probably
a Celtic British king or chieftain of the 6th century AD who fought
against the Saxon invaders of England. The name may also be that of a
Celtic god whose mythology was early confused with the exploits of the
historical figure.
To which the English poet LAYAMON added in his epic narrative Brut at the end of the century.
CHRETIEN DE TROYES (fl. late 12th century) used the court of King Arthur as the setting for his intense, tragic romances of individual knights associated with Arthur.
These in turn influenced the German renderings of the PARSIFAL legend produced by WOLFRAM VON ESCHENBACH
And the Tristan legend produced by GOTTFRIED VON STRASSBURG (both 13th century)
The thirteenth century Vulgate Lancelot -source for much later Arthurian literature, particularly Malory.