In La Tavola Ritonda, the giant pagan ruler of Dolorous Guard. His father was Carone the Great, and his wife was called Nonfizata.
Lancelot conquered the castle by defeating him in combat and slicing off his hand. Federiel surrendered, and Lancelot sent him to Camelot. Federiel journeyed to Mount Nervana, where he found Arthur and his army in the midst of a battle with King Meliadus of Lyonesse. Federiel leapt into the battle and slew ten of Arthur’s men before he was cut down.
Dolorous Guard’s original ruler is called Brian of the Isles in the Prose Lancelot.
Source
La Tavola Ritonda | 1325–1350