Melusine (or Melusina, the Alchemical Siren) is an uncommon figure from European folklore, usually inhabiting streams and rivers, appearing as a mixture of a fish (or serpent, much like a Naga) and a woman. She is sometimes depicted with tails or wings, and is also sometimes referred to as Nixie, or Neck. Melusine was the result of a curse, forever transforming her into a mixture of serpent, fish and woman. This would explain why she is also seen as a mermaid.
As the story is most often told, the cursed maiden is discovered in the forest by Raymond, the Duke of Aquitaine, who begs her to marry him. She agrees, on condition that he never disturb her on a Saturday, when she bathes. Raymond eventually grows suspicious of his young wife, and spies on her- and his shocked reaction to her true appearance reveals his betrayal to Melusine, who transforms herself into a dragon and departs in a shrieking fury with her children. This story can be viewed as a metaphor for sexuality, and the contradictory duality of the female nature as viewed through medieval eyes. Some stories describe her as more of a traditional siren, calling men in from the brecons and causing them to drown. Others depict her as the stealer of children, who beckons to lost children in the night and causes them too, to drown.