Canterlot: a city rife with the unicorn elite. Of that population, 2513 of them are of the Vespers clan. 841 of them have cutie marks in magic. 200 of these live and work at Celestia's School for Gifted Unicorns, and 35 of them serve under Celestia herself.
Only 1 is Celestia's personal student.
Twilight Sparkle is the smartest unicorn of her time. Ever since her entrance exam, she has found her skill rapidly increasing under the watchful eye of the Princess of the Sun. Canterlot, nay, all of Equestria, is watching her, waiting to see who she will become.
Meanwhile, in the distance of space, a great mare of darkness lies trapped within the moon. She watches, burning in anger, as her sister revels in the love of her subjects. But the Night Mare waits and watches as her time draws near. When the stars align, she will be released from her prison and bend Equestria to her will. Eternal night will cloak the world, and she will be master over all.
Suddenly, she feels a weakening. Unscheduled, unnoticed by the Alicorn of the Sun. The seal is torn. The Night Mare pushes against it, but it is not enough. She cannot quite break free. Still, she sees an opportunity. Her magic pushes through the rift, enough to exude her presence, even a bit. There is something to be done here, a plan to be made. Perhaps the sun can be brought down before its time. Though she cannot prevail from the inside, perhaps the seal can be sundered from the outside...
Twilight have I loved, yet Luna have I hated. Yes, the Filly of the Stars will do nicely...
Twilight studies on, utterly unaware of the coming darkness, and the plans of which she is now a critical part.