Once upon a time, in the magical land of Equestria: there were two regal sisters who ruled together and created harmony for all the land. To do this, the eldest used her unicorn powers to raise the sun at dawn; the younger, brought out the moon to begin the night. Thus, the two sisters maintained balance for their kingdom and their subjects -- all the different types of ponies.
But as time went on, the younger sister became resentful. The ponies relished and played in the day her elder sister brought forth, but shunned and slept through her beautiful night. One fateful day, the younger unicorn refused to lower the moon to make way for the dawn.
The elder sister tried to reason with her, but the bitterness in the young one's heart had transformed into a wicked mare of darkness: Nightmare Moon.
She vowed that she would shroud the land in eternal night. Reluctantly, the elder sister harnessed the most powerful magic known to ponydom: The Elements of Harmony. Using the magic of The Elements of Harmony, she defeated her younger sister and banished her permanently in the moon.
The elder sister took on responsibility for both sun and moon, and harmony has been maintained in Equestria for generations since.
"The end," a white unicorn with blue mane said. "Alright Twiley," he shut the book, "now it's time for good fillies to... Twiley?" He blinked in confusion, staring down at the empty bed. An aura of purple energy encompassed his horn and the book. Levitating it, he carried it with him as he hurried out of the room and into the main room. On his flank was a blue shield with six pointed burst of magic in the center.
Sure enough, there was his sister. The little purple unicorn filly with a bare flank was standing on a pile of books on her hind legs. One front leg was resting on a book shelf as the other poked at the books while she looked at the title.
"Twilight?" the stallion asked, "What are you doing?"
"I'm looking for 'Predictions and Prophecies.'" Pulling a book from the shelf and looking at it before tossing it aside. "I know I've heard of those... El-e-ments Of Harmony before." She pulled another book off the shelf and dropped it with the others.
"Twilight Sparkle!" the young stallion said, causing the filly to stop and look at him. "First of all: Spike has worked hard to keep this place organized." His horn glowing, he picked up several of the books she had pulled off and stuck them back into place. "I'm sure he would not appreciate you just tossing the books on the floor." He gave her a firm glare, watching the young unicorn shift and look ashamed. "And second:it's your bed time. You should be upstairs in bed and about to sleep. Not down here rifling through all the books."
"But Shining," Twilight began to whine.
"No buts," Shining Armor cut her off. "Now march your flank upstairs and go back to bed." His features softened as he gave her a small smile. "If it's that important to you, I'll find the book and have it waiting for you in the morning."
"Okay. Good night Shiny." Moving to her brother, she gave in him a kiss on the cheek then started heading back to her room. Shining Armor watches her go then turned back to the shelves. He began to look through the titles, trying to think of where the book might be.
Caught up in his search, he did not hear the steps coming down the stairs.
"Here it is," a raspy voice said, causing the stallion to jump. On top of a ladder stood a small purple dragon with a light green belly holding a book out.
"Spike?" Shining Armor blinked in confusion. "I thought that you had gone to bed already." Reaching out with his magic, he took a hold of the book.
"I had," the dragon replied as he began to climb back down, "but I heard you and Twilight so I came down to help you find the book."
"Thanks," the stallion said with a smile. It faded as his attention shifted from the baby dragon to the book. "Well, maybe I should take a look and see what this book says about The Elements of Harmony since it seems so important to her." Opening the book, he started flipping through the pages. Finally he stopped when he saw the name he wanted.
"See: Mare in the Moon?"
"Mare in the Moon?" Spike repeated. "But that's just an old pony's tale."
Shining Armor just gave a shrug before flipping to the correct section and starting to read:
"The Mare in the Moon: myth from olden pony times. A powerful pony who wanted to rule Equestria. Defeated by The Elements of Harmony and Imprisoned in the moon. Legend has it that on the longest day of the thousandth year, the stars will aid in her escape, and she will bring about nighttime eternal." He chewed his lip and rubbed his chin as he looked at the page. "You don't think..."
"Think what?" Spike asked when the stallion did not continue.
"Spike, take a note. To the princess." Shining waited as the dragon pulled out a piece of paper and a quill. "Dear Princess, while reading a story to my sister, I have come across something very interesting. The story of the mare in the moon may be about Nightmare Moon. If this is the case, then Equestria could be in great danger since she would be about to return and bring with her eternal night. Should this be the case, something must be done. Awaiting your response: your student, Shining Armor."
"Got it."
"Good. Now send it."
"Now?"
"Yes, now."
"I don't know, Shining," the dragon said with shrug. "Princess Celestia's a little busy getting ready for the Summer Sun Celebration. And it's like the day after tomorrow."
"I know," Shining Armor said. "In fact it's the thousandth year of the Summer Sun Celebration." Grabbing the book, he opened it again. "'On the longest day of the thousandth year, the stars will aid in her escape and she will bring about nighttime eternal'" he re-read aloud. "That's means that she may be returning this Summer Sun Celebration. And if that's the case, the princess needs to know."
"But what if it's not?" Spike asked as he rolled the paper.
"Then we don't have to worry," the stallion replied. "And when Twilight reads the story tomorrow, we can tell her we already informed Princess Celestia on the matter. That way she won't be worrying about it and trying to get you to send one herself."
"Oh. Good point." Taking a deep breath, Spike held up the scroll. He then blew out a plume of green fire, causing the paper to burn. A glowing stream of smoke flew up from the dragon's claw and out through the window.
"It's on it's way," Spike proclaimed.
"Good. Let me know when you get a reply." Shining Armor started for the stairs. "I'm going to-"
Before he could finish, a loud belch from Spike got his attention. Stopping, Shining turned to look. Another plume of green flame burst from the dragon's mouth as this time a scroll appeared.
"...That..." he said slowly as he walked back down "was... surprisingly fast."
Spike picked up the arriving scroll, unfurled it and cleared his throat.
"My dearest most faithful student, Shining," he read, "You have always been a diligent stallion whom I could trust. But you simply must get yourself and your sister away from those dusty old books."
"What?"