A Knight of the Round Table related to Lancelot.
When Lancelot and Guinevere were accused of treason, Vyllyers pledged his support to Lancelot and helped him to rescue Guinevere from the stake. In return for his support, Lancelot made him the Earl of Béearn.
After Arthur’s death, Vyllyers joined Lancelot in an abbey at Glastonbury, where he lived as a hermit until Lancelot’s death. After participating at Lancelot’s interment at Joyous Guard, Vyllyers returned to his own lands.
Source
Le Morte Darthur | Sir Thomas Malory, 1469-1470