In Malory, a knight in Arthurís service who was the cousin of Lamorat.
When Lamorat was slain by Gawain and his brothers, Pionel devised a plot to kill Gawain. Guinevere hosted a party, and Pionel poisoned some fruit intended for Gawain. An unlucky knight named Patrise ate the fruit instead of Gawain and died.
The Vulgate Mort Artu calls the same character Avarlan.