A knight that Gawain encountered in his first quest.
Sorlouse was fighting with his brother, Sir Brian of the Forest, over who would chase the hart that Gawain was pursuing. Gawain told them the hart quest was his, and they yielded quickly to him rather than fight him. Gawain sent the two brothers to King Arthur.
Source
Le Morte Darthur | Sir Thomas Malory, 1469-1470