aristocrats whose letters survive in quantity. Brochvael also owns a manuscript of the Comedies of the Greek dramatist Aristophanes. Morfydd is the daughter of Brochvael, and both cousin and future wife of Porius. Rhun is Porius's cousin and foster brother. He is a worshipper of Mithras, a mystery religion practiced in the Roman Empire from about the 1st to 4th centuries AD. His father was Greek. Taliessin is the poet, known as Pen Beirdd Ynys Prydein or Head Bard of the Isles of Britain. Powys compares him to American poet Walt Whitman. Scholars have suggested that there are essentially two Taliessin's: one a professional court poet from the 6th century and the other a mythological figure "associated with other mythological figures, with folklore, and with the idea of “metaphysical, transformational” poetry". The first "a professional poet serving the courts of Welsh princes in the North during the latter part of the sixth century". This Taliesin is briefly mentioned in Historia Regum Britanniae, attributed to Nennius a Welsh monk of the 9th century. The first "historical" Taliesin and Aneirin are to only two early Welsh poets whose work has survived. An important manuscript The Book of Taliesin, or Llyfr Taliesin, contains about sixty Welsh poems, of which twelve are ascribed to the “historical,” Taliesin, a bard, who created praise poems for Urien Rheged and his son Owain ab Urien. There are another fifteen poems which are associated with the "legendary" Taliesin; these texts refer to a wide-ranging time trans-shifting shape-shifting all-knowing mythological being, who is described as both timeless and eternal. Another important Taliesin text is the Ystoria Taliesin, Hanes Taliesin, which contains Welsh prose and poetry, about and, claiming to be, by Taliessin. Taliessin is also mentioned in Welsh triads, and in the beginning of Culhwch and Olwen. The Henog: Powys created Sylvannus Bleheris, Henog of Dyfed, author of the Four Pre-Arthurian Branches of the Mabinogi concerned with Pryderi, as a way linking the mythological background of Porius with this aspect of the Mabinogion. Amherawdr (Emperor) Arthur the Brythonic ruler of Britain is only a minor character in Porius. Arthur is a legendary British leader of the late 5th and early 6th centuries, who, according to medieval histories and romances, led the defense of Britain against Saxon invaders in the early 6th century. The details of Arthur's story are mainly composed of folklore and literary invention, and his historical existence