When a group of mages gather to set in motion their own events, they find a creature of grey.
When Nightmare Moon was cleansed, it was not defeated, only sealed away in the armor that was ruined in the cleansing power of the Elements of Harmony. With the help of a group of Mages she now plans to conquer not just Equestria, but also the world that a new creature she pulled in to help her as well.
There is just one small problem to that plan. The Spell misfired, she got the creature she wanted, but it had the gumption to exercise free-will and follow his own morals, it doesn't help that he has vanished. After all, how can one hide A Human in a world of Ponies? What is a nightmare to do?