Two entries with the name Mathamas.
Mathamas
Matamas
The lord of a tower near the Fairies’ Fountain. Mathamas hated Arthur.
While adventuring in the forest with Guinevere, Dodinel and Sagremor (Sagramore) embarked on a quest to procure some rations from Mathamas. Dodinel was diverted along the way, but Sagremor entered Mathamas’ hall and boldly demanded food. Mathamas responded by ordering his knights to attack Sagremor, and after an exhausting battle, Sagremor was imprisoned.
Mathamas’ daughter kept Sagremor from starving until Gawain showed up, defeated Mathamas, and forced him to release Sagremor.
He is probably identical with Mathamas du Recet.
Source
Vulgate Lancelot | 1215-1230
Mathamas
Mathucus
A king of the Saxons.