There follows an account of a great monstrous beast, of the fear of the Britons and how, by Gwydion's skill and the grace of God, the trees marched to battle: then follows a list of plants, each with some outstanding attribute, now apt, now obscure;
The poem then breaks into a first-person account of the birth of the flower-maiden Blodeuwedd, and then the history of another one, a great warrior, once a herdsman, now a learned traveller, perhaps Arthur or Taliesin himself.
According to a summary of a similar story preserved in Peniarth MS 98B (which dates from the late sixteenth century) the poem describes a battle between Gwydion and Arawn, the Lord of Annwn.
The Cad Goddeu, which is difficult to translate because of its laconic allusiveness and grammatical ambiguity, was the subject of several nineteenth-century speculative commentaries and English renderings.
Graves argued that the original poet had concealed druidic secrets about an older matriarchal Celtic religion for fear of censure from Christian authorities.
Marged Haycock and Mary Ann Constantine reject the idea that Cad Goddeu encodes ancient pagan religions as Graves believed but rather see it as a burlesque, a grand parody of bardic language.
[7] Soviet and later Russian rock group Aquarium recorded a song "Kad Goddo" on their album Deti Dekabrya, 1986, quoting some of the lines directly from the poem.
Tim Powers has the protagonist of his book The Drawing of the Dark, Brian Duffy, utter a few verses of the Cad Goddeu to evoke ancient beings to fight with him.