The Black Knight appears in various forms in Arthurian legend.
In Sir Perceval of Galles (written in the early 14th century), the Black Knight jealously tied his wife to a tree after hearing she had exchanged rings with Perceval. Perceval defeated the black knight and explained that it was an innocent exchange.
A supernatural Black Knight is summoned by Sir Calogrenant (Cynon ap Clydno in Welsh mythology) in the tale of Yvain, the Knight of the Lion. The Black Knight bests Calogrenant, but the Black Knight is later killed by Ywain (Owain mab Urien) when he attempts to complete the quest that Calogrenant failed.
A black knight is the son of Tom a'Lincoln and Anglitora (the daughter of Prester John) in Richard Johnson's Arthurian romance, Tom a'Lincoln. Through Tom, he is a grandson of King Arthur's, though his proper name is never given. He killed his mother after hearing from his father's ghost that she had murdered him. He later joined the Faerie Knight, his half-brother, in adventures.
A black knight is also mentioned La Morte D'Arthur: The Tale of Sir Gareth (book 4) as having been killed by Gareth when he was traveling to rescue Lyonesse.