In Guillaume le Clerc’s Fergus, a mountain in Scotland, also called the Black Mountain.
This mountain was inhabited by the fearsome Black Knight. Arthur’s knight Fergus journeyed to Nouquestran to obtain a magic horn and wimple from the Black Knight, and he succeeded.
Nouquestran was also said to be one of Merlin’s haunts. M. D. Legge has suggested Mount Rubers Law, a hill in the Scottish Borders, as the geographic location that Guillaume had in mind.
Fergus | Guillaume le Clerc, 1200-1233