Prolouge: Decent into Darkness

Once upon a time, there was a beautiful land known as... Equestria. Ruled by two Alicorn Princesses, it was a peaceful Utopia. The eldest of the two controlled the sun, the youngest the moon. And all was peaceful, as the Princesses ruled with kindness but firmness. Until one fateful day... the youngest had enough.

"Celestia!" Luna shouted as she stomped towards the throne, "You and I need to have words!"

"Well, sister," Celestia stood from her seat, her hair sparkling in the sunlight, "What be this thou wanted to-"

"CAN IT!" Luna shouted, "I'm sick of this! I've done nothing but watch you rule the kingdom with kindness and the occaisional joke, while I just watch ponies sleep and make love!"

"Sister, you're..."

"I know what I said sounded creepy, didn't think it through enough!" Luna stamped her hoof, "I'm tired of being second fiddle! I'll be taking over duties you've held to yourself!"

"Sister, you can barely raise the stars unassisted," Celestia noted, "What makes you think you can handle raising the sun?"

"I know I don't. But raising the sun doesn't make you a QUEEN, Celestia!" Luna shouted, "If anything, I'm more skilled in running this global country of Equestria!"

"Well, sister, I'm afraid that our agreement, which you signed, doesn't allow you to take over duties unless you can raise the sun," Celestia replied, "We'll talk abou this another-"

"BUCK THE AGREEMENT!" Luna shouted, her eyes narrowing into slits, and her skin turning dark, "IF I CAN'T RAISE THE SUN, NO ONE WILL!"

"But Luna... how will you bring about Daytime without the sun?" Celestia replied, nervousness dripping from her voice.

"Quite simple, really..." Luna spoke, "If I can't bring about Daytime, I'll just make it like it never existed. From this day forth... THE NIGHT WILL LAST FOREVER!"

"But Luna-" Celestia spoke, only for the mane of her sister to toss her aside.

"It's not Luna anymore," The Princess spoke, "I am this world's new queen... no... God-Empress, NIGHTMARE MOON!"

"You can't do this!" Celestia shouted at the Transformed Luna, eyes full of terror, "I'm your sister, remember! Sisters stick together, right?"

"Our parents told us this, but I now see through this tripe!" Nightmare Moon spoke, "And if I have to kill you to gain my position... then so be it!"

And suddenly, a massive rainbow hit the Princess, enveloped her, and disappeared, leaving nothing.

"What was that?" Celestia turned to see a group of the guardmares, those she remembered as Twilight, Surprise, Posey, Firefly, Sparkler, and Applejack the 3rd, wearing the Elements of Harmony.

"Sorry, Princess," Posey spoke, "She was too dangerous."

"Well, on the bright side, I sent her to the MOON!" Surprise added, "She'll love it there!"

"My friends," The Princess got up, "What you did was... harsh, but necessary. However, her imprisonment will only last 1000 years."

"What!" Everyone shouted.

"Your Highness, if I may object," Twilight spoke, "We may need to live that long to counter-"

"You won't," Celestia sighed, "When Nightmare Moon returns from her imprisonment... you will be long gone. But I already have a plan for the Elements of Harmony... and your descendents. Let this be written down; On the longest day of the thousandth year, the moon's Avatar will return and try to plundge the world into darkness. But where there is darkness... there will soon be light."

On the moon, Nightmare stood, gazing on the planet above.

"One day soon, Celestia, I shall return... and finish what I started!" The princess shouted, "And your precious Elements will not stop me..."

And so, Nightmare Moon became a legend, and Celestia controlled the night and day. Nightmare swore to return on the longest day of the thousandth year since her banishment, and plunge her world into everlasting night. but Celestia had a plan...

Her eyebrows raised in confusion, and she asked herself the question...

"What was the plan?" Twilight Sparkle, the 500th generation reincarnation of the Guardspony Twilight asked.