Three entries with the name Margon.
Margon
Marganor, Margons, Margouns
The wine steward of the Saxon king, Pignoras. He fought against Arthur’s forces at the second battle of Clarence, and was killed there.
Source
Vulgate Merlin | 1220-1235
Margon
Margun
A wicked giant whose brothers were Ulian and Durkion (Durkan).
The brothers served Lord Karedoz of Malmontan, and all of them were slain by Arthur’s Sir Tandareis.
Source
Tandareis and Flordibel | Der Pleier, 1240-1270
Margon
The King with a Hundred Knights in the Third Continuation of Chrétien’s Perceval.
Before he was known by this name, he led an siege on the castle of the Sore Pucelle in an attempt to force the lady to marry his son. His son, Cargrilo, was taken prisoner by the Sore Pucelle, and was catapulted to his death when Margon killed the Sore Pucelle’s lover.
Margon was eventually defeated by Gawain, the Sore Pucelle’s champion, and sent to Arthur’s court. During the journey, he rescued his sister, the Lady of Malehaut, from Gorgari, an abductor. Arriving at Arthur’s court with a hundred knights in tow, he was given his more common designation. Arthur appointed him to the Round Table.
His name may reflect Malaguin, the King with a Hundred Knights in the Vulgate Lancelot.
Source
Third Continuation of Chrétien’s Perceval | Manessier, c. 1230