In Ulrich’s Lanzalet, a beautiful woman from the enchanted island of Thyle.
She committed some breach of courtly etiquette and was sentenced to take the form of a dragon until kissed by the best knight in the world. She hunkered in a British forest until Arthur’s knight Roidurant came along. Clidra begged him to kiss her, but he instead fled. Later, he related the story to Lancelot, who came to the forest, kissed the dragon, and restored her to her original form.
An analog to this story is found in the Fearsome Kiss adventure of Le Bel Inconnu.
Lanzelet | Ulrich von Zatzikhoven, c. 1200