Thomas the rhymer is a fictional take on the quasi-historical figure of the same name. The Thomas the rhymer ballad shares a decent amount, historically, with the ballad of Tam Lin.
Brief plot summary
Thomas the rhymer tells the story of the minstrel Thomas, his seven yeras of captivity in Faerie, and his eventual return to the mortal world. Taken in by an elderly couple both before and after his imprisonment, each segment of the story is told from the point of view of a different character.