Culhwch and Olwen preserves an Arthurian world very different from the later courtly romances of Lancelot and the Grail. Arthur appears as a powerful British war-leader surrounded by an enormous company of warriors, hunters, magicians and figures whose abilities often belong to an older heroic and folkloric tradition.

The story begins when Culhwch rejects the daughter of his stepmother. She lays a destiny upon him that he will marry no woman except Olwen, daughter of Ysbaddaden Pencawr. Culhwch seeks the aid of his cousin Arthur, who binds members of his court to the quest.

When Culhwch reaches Ysbaddaden's stronghold and asks for Olwen, the giant sets an extraordinary bride-price. The tasks include acquiring rare animals, weapons and objects, freeing Mabon son of Modron, obtaining the cauldron of Diwrnach, gathering impossible quantities of seed and securing the comb, scissors and razor carried by the enchanted boar Twrch Trwyth.

The search for Mabon sends Arthur's men through a chain of ancient animals whose memories stretch further and further into the past. The hunt of Twrch Trwyth then becomes one of the tale's largest action sequences, ranging across Ireland, Wales and Cornwall before the boar is driven into the sea.

Once the required objects and tasks have been secured, Ysbaddaden is shaved and forced to acknowledge that Olwen belongs to Culhwch. Goreu son of Custennin kills the giant, and Culhwch and Olwen marry.

The work is important to Mythopouch because it preserves an early Welsh form of Arthurian tradition before the major development of French courtly romance. Its Arthur, Cai, Bedwyr, Gwalchmai, Mabon and other figures can therefore differ sharply from their later medieval counterparts.

The 1842 source witness used here was translated, edited and annotated by Lady Charlotte Guest. Her edition is valuable as a public-domain English witness, but it belongs to 19th-century scholarship and uses spellings such as Kilhwch that differ from modern Welsh forms. Mythopouch uses Culhwch as the principal modern display spelling while retaining Guest's witness for source checking.