The Book of Taliesin (Welsh: Llyfr Taliesin) is one of the most famous of Middle Welsh manuscripts, dating from the first half of the 14th century though many of the fifty-six poems it preserves are taken to originate in the 10th century or before.
The volume contains some of the oldest poems in Welsh, possibly but not certainly dating back to the sixth century and to a real poet called Taliesin.
Welsh mythology, also known as Y Chwedlau (Welsh for 'the legends'), consists of both folk traditions developed in Wales, and traditions developed by the Celtic Britons elsewhere before the end of the first millennium. As in most of the predominantly oral societies Celtic mythology and history were recorded orally by specialists such as druids (Welsh: derwyddon). This oral record has been lost or altered as a result of outside contact and invasion over the years. Much of this altered mythology and history is preserved in mediaeval 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 ninth-century Latin historical compilation Historia Brittonum (History of the Britons) and Geoffrey of Monmouth's 12th-century Latin chronicle Historia Regum Britanniae (History of the Kings of Britain), as well as later Welsh folklore, such as the materials collected in The Welsh Fairy Book by William Jenkyn Thomas (1908).
Aeron was a kingdom of the Brythonic-speaking Hen Ogledd (English: Old North), presumed to have been located in the region of the River Ayr in what is now southwestern Scotland. It existed during the post-Roman era, perhaps earlier, and disappeared before or during the 7th-century conquest of the region by the ascendant Kingdom of Northumbria.
Aeron is incidentally mentioned in the Book of Taliesin in poems of praise to Urien of Rheged. It is the homeland of several heroes in the Book of Aneirin. The families of several of these heroes also appear in royal genealogies associated with the genealogies of the better-known kings of Alt Clut who lived in southwestern Scotland. This, taken together with the phonetic similarity of Aeron and Ayr, suggests the location of Aeron.
Urien ap Cynfarch Oer (Welsh pronunciation: [ˈɨ̞riɛn ap ˈkənvarχ oːɨ̯r]) or Urien Rheged (Welsh pronunciation: [ˈɨ̞riɛn ˈr̥ɛɡɛd], Old Welsh: Urbgen or Urbagen, Old Welsh pronunciation: [ɨ̞rβ(ə)ˈɣɛn]) was a powerful sixth-century Brittonic-speaking figure who was possibly the ruler of the territory or kingdom known as Rheged. He is one of the best-known and best documented of the British figures of the Old North. His kingdom was most likely centred around the Solway Firth. According to the section known as the "Northern History" of the Historia Brittonum (c. 829–30 AD), Urien gained a decisive advantage in a conflict against the Anglo-Saxons in northern Britain while leading an alliance with three other kings: Rhydderch Hen, Gwallog ap Llênog, and Morgan. The alliance led by Urien penned the Anglo-Saxons in at Lindisfarne, though this siege came to an abrupt end when Urien was murdered on the orders of his erstwhile ally Morgan.
The most secure evidence for his existence comes the Historia Brittonum and eight praise-poems in Middle Welsh orthography dedicated to him surviving in a fourteenth-century manuscript. Despite their being found in later orthography, the poems may possibly reflect early material, even material contemporaneous to Urien. One of these poems is explicitly attributed to the famed poet Taliesin in the manuscript. The "Northern History" in the Historia Brittonum also roughly synchronises Taliesin's career to the reign of Ida of Bernicia (547 × 549). Some of the Beirdd y Tywysogion (c. 1100–1283) also allude to this strong association between Taliesin and Urien. The panegyric attributed to Taliesin concerning Urien is particularly significant because if it truly originates in the sixth century it, together with the poetry attributed to Aneirin, would be the earliest vernacular post-Classical European literature.