After running through some ideas, my mind eventually settled on one pony who was always 'up to no good': the power-hungry, two-faced, devious filly, Cozy Glow. She proved to be both an effective and terrifying villain, not just for how she managed to set her plans in motion without being detected, but also for the fact that she nearly succeeded in draining all the magic from Equestria when she was only a filly, and a pegasus, at that. She didn't even need magic to accomplish her goals, the little demon…
So, what is she plotting now? Who knows? It could be another plot to overthrow Equestria, or even steal from a cookie jar. Whatever it is, Cozy's guaranteed to approach it with the same level of cunning and slyness.