Thousands of years ago Princess Luna grew jealous of her sisters' popularity and transformed into the dark visage of Nightmare Moon, but is that all that happened?
Twilight has been a tiny, hardworking student for many years, willingly deciding to stay two hooves tall after discovering a love for the adventures and challenges that came with it. How will the rest of the mane six and Nightmare Moon react to her?
'The Mare In The Moon' wasn't the only legend that Twilight read that fateful day. And just like the aforementioned legend this one was also true. it just happened earlier than the other, and Twilight is 'dead' center of the legend.
Twilight Sparkle is the result of centuries of careful manipulations by the Princess of Equestria with the end goal of freeing the Mare in the Moon. Of course, it is difficult to affect ponies from space; control of dreams was most helpful.