Centuries ago...when humans and mermaids lived together in harmony, the mermaids decided to take advantage of the kindness of the humans, later invaded and killed half of the human population for their own good. That's when the humans cast a spell on the mermaids which decreased their population one by one, bashing them into the deep oceans.......away from mankind and also broke down their ability to have legs whenever they tried to come to the surface. But.....the curse can be broken.............only when a human with special powers is sacrificed and his/her blood is made to spread throughout the mermaid empire.