Deon, Deu, Dieu, Does, Doon, Dos, Due, Landinas?
The son of Ares and the father of Arthur’s Sir Girflet and Lorete (or Lore), and Uther’s forester, according to Chrétien de Troyes.
He served as Arthur’s castellan of Cardueil and, later, London. He fought against the Saxon invasion at the beginning of Arthur’s reign. Malory calls him ‘Cardol’ (Cardueil), confusing his home with his name.
This is according to D.D.R. Owen’s translation, but I suspect that “Do” was either a variant of or a scribe’s error for “Dieu”. Else the post-Chrétien writers confused a human character’s name with that of the Deity.
Sources
Erec | Chrétien de Troyes, late 12th century
First Continuation of Chrétien’s Perceval | Attributed to Wauchier of Denain, c. 1200
Vulgate Merlin | 1220-1235
Arthour and Merlin | Late 13th century
Le Morte Darthur | Sir Thomas Malory, 1469-1470