Caer Dathyl

Caer Dathyl was a Welsh fortress in Arfon in northern Gwynedd referred to in the Fourth Branch of the Mabinogi, the Tale of Math fab Mathonwy. Its precise location is currently unknown and has been the subject of speculation. In the tale, it is the seat of Math's court to which Gwydion ap Don takes the hero Lleu Llaw Gyffes.

In fiction

Caer Dathyl is the location from which the High King of Prydain ruled in the stories told in Lloyd Alexander's Chronicles of Prydain. It was built by the Sons of Don in the north of Prydain, among the Eagle Mountains, intended to protect Prydain from further conquests by Arawn of Annuvin. A tall fortress on a hill dominated the cottages, shops and other buildings in the valleys below it; the stones used to make the fortress had a color similar to gold.

The fortress of Caer Dathyl was not only a place of defense and a seat of royal power, but also served as a repository of literature and art of every variety from throughout Prydain. A grove of hemlocks was planted in one of its courtyards above the burial mounds of past kings and heroes, and storehouses preserved the treasures of craftsmen collected from every corner of the land.

The Chief Bard also resides at Caer Dathyl, where he maintains the Hall of Lore and the Hall of Bards, both of which store many of the historical documents, songs, poems, and other items of literature. Access to the Hall of Bards was limited to official bards, though other people were permitted within the Hall of Lore.

In "The Book of Three", Prince Gwydion surmises that Arawn's war leader, the Horned King, intends to destroy Caer Dathyl with the army he rallied in the southern realms of Prydain. The story's protagonist, Taran, sets out with his companions to warn the people of Caer Dathyl of the attack, though he failed to reach the fortress before the vigilant Sons of Don met the Horned King's army in battle in the valley beyond Caer Dathyl. The battle ended decisively in the Sons of Don's favor when the Horned King himself was slain, sparing Caer Dathyl itself from any damage. After the battle, Taran and his companions were welcomed as heroes by the High King Math, and saw much of Caer Dathyl before returning home to Caer Dallben.

Caer Dathyl saw battle again in the final book of the series, "The High King". Gwydion designated it as the rallying point for all the armies in Prydain who were loyal to the Sons of Don, though only the armies of the northern realms and the Free Commots made it there before a fierce battle ensued. Pryderi, king of those western domains that were loyal to the Sons of Don, came to Gwydion and Math, demanding they either join him and Arawn as allies, or fight them. His ultimatum was rejected, and the next morning his armies faced the defenders of Caer Dathyl in the snow-covered valley before the fortress, led by Gwydion, the Chief Bard Taliesin, and Taran.

As evening approached, Pryderi's forces broke ranks and retreated, but were then joined by an army of Huntsmen of Annuvin and deathless Cauldron-Born sent from Annuvin. The Cauldron-Born slew the High King Math inside the gates of the fortress, and throughout the night they leveled Caer Dathyl in its entirety, killing all who stood in their way.

After the conclusion of the war, Taran determined to rebuild Caer Dathyl, including the Hall of Lore and Hall of Bards, hoping to recover the knowledge preserved there as well as providing a place for future learning to be stored. This goal was eventually fulfilled during his reign as High King of Prydain.