This villainous knight was a retainer of the king of Norgales.
Lancelot met Phelot’s wife hurrying after her falcon, whose luned had got entangled in a tree. She begged Lancelot to recover the bird, lest her husband slay her for its loss. Although protesting that he was “an ill climber”, Lancelot stripped to his shirt and beeches, climbed the tree, and threw down the hawk.
Barely had the lady recovered it when Sir Phelot came charging out of ambush to reveal that his wife had acted on his orders in setting up a ruse to trap Lancelot up a tree without arms and armor and kill him.
Lancelot killed Phelot instead, with the help of a tree branch, and left the lady in a swoon.
Source
Le Morte Darthur | Sir Thomas Malory, 1469-1470