Melusina
The most famous of the fays of France. Being condemned to turn into a serpent from the waist downwaist downwards every Saturday, she made her husband, Count Raymond of Lusignan, promise never to come near her on a Saturday. This prohibition finally exciting his curiosity and suspicion, he hid himself and witnessed his wife's transformation. Melusina was now compelled to quit her mortal husband and destined to wander about as a spectre till the day of doom. It is said also that the count immured her in the dungeon of his castle. :