Two entries with the name Avarlan.
Avarlan
Arnalon, Avarlon
In the Vulgate Mort Artu, a knight who hated Gawain.
He poisoned some apples, which he expected Guinevere to give to Gawain at dinner. Guinevere, however, offered the fruit to Gaheris of Carahew instead. Gaheris died and Guinevere, completely innocent, was accused of murder. Lancelot eventually acquitted her.
Malory renamed the character Pionel.
Source
Vulgate Mort Artu | 1215-1230
Avarlan
A castle in Britain where Gaheris, Gawain’s brother, fought a duel against Baudon, the Red Knight. Gaheris was victorious.
Source
Post-Vulgate Suite du Merlin | 1230-1240