Herzog Ernst, one of the best medieval German “Spielmannsepen,” or Byzantine Narratives, from ca. 1170/1180 (ms. A), and fully developed only by ca. 1220/1230 (ms. B).
See the PDF of the English translation The legend of Duke Ernst [5.9MB PDF] / translated, with an introd., by J. W. Thomas and Carolyn Dussère (Lincoln: University of Nebraska Press, 1979).