Fenice's nurse was named Thessala after the country of her birth.
Chrétien de Troyes assures us that Thessaly was a land of traditional charms and devilish enchantments; Thessala was certainly adept at brews. Not only could she cure diseases and heal wounds of all kinds, she also knew how to prepare a potion that, when Emperor Alis drank it on his wedding night, caused him ever afterward to fall asleep and dream so convincingly of enjoying his wife that he believed he was doing so in face, while she lay untouched beside him.
Later, Thessala made Fenice a potion that caused her to seem dead long enough for Cligés to spirit her away. During Fenice's shammed illness preparatory to this ruse, Thessala also showed plain old human cunning in fooling the doctors by substituting the urine of a woman who really was mortally sick for that of her mistress.