My defeat was a… Humbling experience. I knew what a threat Twilight posed to my plans and all the signs were there of her knowledge on what my sister and I have done. Still, I was too busy being proud of her. Now she has become something I thought I would never have again. A rival worthy of my full attention.

Let the chess game of the gods begin. ~Celestia's thought on Twilight seizing the throne.

Evil and Darkness may often dance together the two are not wed with Luna being a shining example of this. However the same is true for Light and Purity. Celestia harbors something far more foul then an alter ego that Luna had conjured. It is sickly and pervading, latching its ghastly claws into her very being. What exactly it is she does not know nor is she even aware of it, but should her life be in danger this parasitic disease will come to the surface and seek to defend its host. The longer it stays the more it changes, not just in itself but also the host in both physical and mental aspects. For now however it simply sits and gathers its strength from the alicorn's weakening psyche until it will finally just consume Celestia in her entirety.