In Chinese mythology, fox spirits (狐狸精) are foxes that cultivate supernatural powers and can shapeshift into beautiful women to seduce men. The most famous is 妲己 (Dájǐ) from the novel Investiture of the Gods.
usage
When used as an insult toward a woman, 狐狸精 implies she seduces other women's husbands. It's a strong insult — handle with care.