Seleyses, Selises, Selyses
Nephew of the King with a Hundred Knights and a Knight of the Round Table.
He won honor at a tournament at Camelot and fought at the Leverzep tournament. He was infatuated with Isolde.
When Lancelot and Guenevere were accused of treason, Celices pledged his support to Lancelot and helped him to rescue Guenevere from the stake. He fought alongside Lancelot when Arthur laid siege to Joyous Guard and, later, Benoic (Benwick).
In return for his support, Lancelot made him the Earl of Marsan.
Sources
Palamedes | c. 1240
Prose Tristan | 1230-1240,
Le Morte Darthur | Sir Thomas Malory, 1469-1470