The loathly lady, is a tale type commonly used in medieval literature, most famously in Geoffrey Chaucer's The Wife of Bath's Tale. The motif is that of a woman who appears unattractive but undergoes
"Lady, I will be a true and loyal husband." Gawain and the loathly lady in W. H. Margetson's illustration for Maud Isabel Ebbutt's Hero-Myths and Legends of the British Race (1910)