What is "bisclavret"

"Bisclavret" ("The Werewolf") is one of the twelve Lais of Marie de France written in the 12th century. Originally written in French, it tells the story of a werewolf who is trapped in lupine form by the treachery of his wife. The tale was popular and was reworked as The Lay of Melion, and is probably referenced in Sir Thomas Malory's Le Morte d'Arthur with the story of Sir Marrok, who has a similar story.