Carbonek: The Grail Castle of Arthurian legend, was an otherworldly heaven guarded by angels and wondrous spirits who's unearthly song was beautiful beyond imagining. The castle housed the Grail, a holy vessel, said to be the Cup of the Last Supper, which contained healing spiritual sustenance. Lancelot was ferried to Carbonek on a ghostly ship without a captain or crew and permitted a distant vision of the sacred chalice because of his courageous spirit. His love ove Guinever forbade a complete vision.
--From the Encyclopedia of Mythology by Arthur Cottrell

Also Taliesin, prophetic poet. Wales's greatest bard. Was gifted with all-seeing wisdom after drinking from Ceridwen's cauldron. Fortold coming of the Saxons and oppression of Cymry (Wales). (I'm not sure this name hasn't been used by a group in the past.)

Ceridwen - Welsh goddess of fertility. To compensate for giving birth to the ugliest man in the world, she boiled a cauldron of knowledge. The tale gets rather messy after that.