Headcannon time:
 
When Twilight received the powers of the princesses, she absorbed some of Luna’s Nightmare Moon corruption, AKA the thing we see disappear after S1 EP 2 (Spoiler alert, sorry guys). Causing her transform into Nightmare Sparkle. Even though Tirek stole her powers and at the end Equestria’s magic was brought back to their original owners (spoilers again). Celestia, Luna and Cadences’s was never fully regained, the magic had actually returned mostly to Twilight since she technically owned them at that point. So yadi yadi yada Twilight turns evil, she destroys her castle (please happen) and with the powers of “FRIENDSHIP” things are settled.
 
That’s the gist of it, explained in a crappy summry, but in actuality we thought about this more and want to do a comic about it. Filled with action, comedy, lazer light shows, and maybe a romance scene with Flash sentry kissing Twilight passionately (kidding kidding…. or not)
 
We’ll see, “it could happen”.