Son of King Harlon.
"rode into a forest, and held no highway. And... he saw a fair plain, and beside that a fair castle".
A tournament was in progress between the castle knights, in black, and other knights, in white. Lancelot entered on the side of the castle (black) and was defeated and shamed. In sorrow he rode on through a deep valley, past a mountain, and to a chapel where a recluse lived. She explained to him that the tournament had a spiritual meaning. Although the combatants “were earthly knights”, the
tournament was a token to see who should have most knights, either Eliazar, the son of King Pelles, or Argustus, the son of King Harlon. But Eliazar was all clothed in white, and Argustus... in black, the which were [over]come.
The knights in black symbolized sinners, those in white virgins and good men.
Finding nothing more about King Harlon and his son Argustus, I hypothize that their country was in northern Logres or southern Scotland, so that Harlon’s son and Pellam’s could convenietly arrange their tournament. The last specific site Lancelot appears to have visited was the place I have called “Chapel of the Demon”. At least two, perhaps three, days of travel seem to have passed between the time Lancelot left the chapel and the time he came to the tournament; it was hardly, however, uninterrupted travel. The similarity of the names suggests that possibly Harlon’s son Argustus was also Aguarus, the nephew of the dead man whom Lancelot found in the chapel.
Vulgate Queste del Saint Graal | 1215-1230
Le Morte Darthur | Sir Thomas Malory, 1469-1470