Feldenak
In the Alliterative Morte Arthure and Malory, a Roman warrior who, seeking to avenge the death of his comrade Gaius Quintillianus, tried to kill Gawaine. Gawaine slew him.
He is known in the earlier chronicles as Marcellus Mucius.
Source
Alliterative Morte Arthure | c. 1400
Le Morte Darthur | Sir Thomas Malory, 1469-1470