Arpian of the Strange Mountain, Harpin
A Knight of the Round Table from the Narrow Mountain or the Strange Mountain.
He embarked with the others on the Grail Quest, during which he joined company with Agamenor and Amatin the Good Jouster. All three knights hated Lancelot’s family, so they attacked Galahad, but were defeated.
Later, they assaulted Acorante the Agile and Danubre the Brave, Lancelot’s cousins. Arpian was slain by Danubre.
Source
Post-Vulgate Queste del Saint Graal | 1230-1240
