Melusine

Of European folklore, the Melusine is a legendary creature that looks like a woman with the lower body of a serpent or fish. She's also considered a type of mermaid with double tails. Some regard her as a form of water dragon. She's often associated with death and omens, and many noble houses such as Anjou, Lusignan and even the Plantagenet believe that when a Melusine figure appears, its an omen of death. The Melusine is also considered a water fairy, and has links with the fairy tale characters in stories "The Little Mermaid" and "The Swan Maiden". 

It's early origin appears in a 14th century fantasy story "Roman de Melusine" by Jean d'Arras (1393). It concerns a girl named Melusine with a human father and a fairy mother. She was cursed by her mother Prisine into turning into half a reptile on every Saturday. Her only way to break this curse was for a man to love her and accept who she was during Saturdays. Count Raymondin fell in love with her but she couldn't reveal her secret to him. They both got married and had children. The problem is that Raymondin was becoming more suspicious of his wife because he never knew what she did on Saturdays. He spied on her and saw that her lower body was reptile, and he couldn't love her anymore. The bitter husband went further and became malicious to humilate his wife in public by calling her a monster. Now because of this, Melusine was doomed to become a whole reptile for the rest of her life. She became a dragon. 

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