A Cornish earl and knight, Fergus
was but a young man, and late come into his lands
when Sir Marhaus came along to kill his troublesome neighbor, the giant Taulurd. When next we meet Fergus in Malory, he is one of Tristram’s knights and acts as a messenger for Tristram (Tristan). He helped effect a reconciliation between Tristram and Isolde after a quarrel.
Later we learn that he become a fellow of the Round Table. With Tristram, Dinas, and others, Fergus grieves for Prince Boudwin and refuses to raise hand against Sir Sadok for helping Boudwin’s wife Anglides escape with her son. His last appearance seems to be at the attempt to heal Sir Urre.
The Vulgate has at least one Fergus, but I am not sure he can be identified with Malory’s character.
Prose Tristan | 1230-1240
Le Morte Darthur | Sir Thomas Malory, 1469-1470