Mestra

In Greek mythology, Mestra (Μήστρα, Mēstra) was a daughter of Erysichthon of Thessaly. Antoninus Liberalis called her Hypermestra and Erysichthon Aethon.

Family
Mestra was the mother of King Eurypylus of Cos by Poseidon. According to Ovid, she was married to the thief Autolycus.

Mythology
Mestra had the ability to change her shape at will, a gift of her lover Poseidon according to Ovid. Erysichthon exploited this gift in order to sate the insatiable hunger with which he had been cursed by Demeter for violating a grove sacred to the goddess. The father would repeatedly sell his daughter to suitors for the bride prices they would pay, only to have the girl return home to her father in the form of various animals. Mestra's great-granduncle Sisyphus also hoped to win her as a bride for his son Glaucus although that marriage did not take place.

Ultimately, Poseidon carried away Mestra to the island of Cos. "'And earth-shaking Poseidon overpowered her far from her father, carrying her over the wine-dark sea in sea-girt Cos, clever though she was; there she bore Eurypylus, commander of many people.'"