Prologue
Gentle beams of sunlight washed the halls of Canterlot castle, painting the walls and floor in a pale, golden light. Soon it would be time to set the sun, but for now, Queen Celestia was intent on strolling through the halls of her home. As she passed through a smaller corridor, it's rooms harboring storage shelves of spells and books, she heard a faint clatter come from a room whose door was marked with a warning sign.
Her ears pricked at this, and she felt a burst of anxiety sprout in her. The sound had come from the room in which she stored spell-books on the dark magic of Equestria. She took a tentative step forward, taking sudden caution to ensure she made no noise herself, so as to not alert the potential trespasser of her presence. Carefully, she leaned forward and looked through the small gap of the barely open door.
Inside, was of course walls lined with spell-books, potion vials and artifacts. In the center of the dimly lit room was a table, on which was sprawled various scrolls and book pages, all scattered about in a chaotic manner. Sat at that table, surrounded by the various enchanted pages and dark cloud of black magic spilling from her horn, was Celestia's own faithful student, Sunset Shimmer.
The brief pang of fear in Celestia bubbled into a sickening feeling of dread, and betrayal. Sunset, and any student whom Celestia had taken under her wing, were forbidden from studying dark magic. It was in part from the dangerous nature of the magic itself, and in other part the intention of dark magic. The way those spell books and artifacts called out to ponies, enticing them, seducing them, and then corrupting them... She couldn't let that happen again- she WOULDN'T let that happen again.
Forgoing all intentions of staying quiet, Celestia slammed open the door to the small room. The bang of the wooden door against the wall startled Sunset, who dropped the book she was so closely studying, and whipping around to see what, or who caused the disturbance. The unicorn's face quickly changed from frustration to dread as she saw the Alicorn queen standing in the doorway. Her massive white wings drawn, closing any remaining gaps in the entrance that her mane and body didn't already.
The voice that Sunset had been hearing for those past weeks shrieked in her mind, raging and calling her to "Take action now!" "Fight her now!" "Take over now!" Sunset yelped, raising a defense hoof to her head, the sharp words stinging and stabbing the inside of her skull. Celestia's guard immediately dropped as she saw Sunset clutch her head in pain, and the dark cloud of magic begging to swirl and boil into a fierce storm. Celestia knew she had only moments to stop Sunset, before the magic that was holding her fully took over.
The Alicorn rushed to Sunset, and gripped her shoulder, pulling the smaller Unicorn into an embrace. It was in part because she feared for the safety of her student, and in part because of what she needed to do next. Celestia's horn lit in a heavenly glow as her magic sparked, and reached its way to the dark cloud surrounding Sunset. The storm resisted, lashing back at Celestia, and sending tiny sparks of magic flying off into the room.
Celestia ignored this, and concentrated harder, pushing her magic into the cloud. Her skull rang as she did so, as if she was pushing head first against a mountain side. Still, she persisted, her magic sparking and sputtering its way through the black magic, until finally reaching the tip of Sunset's horn. At this Sunset cried out, and leaned into Celestia harder. Celestia was sure she felt the warmth of tears against her chest as Sunset cried out.
The voice was screaming, unearthly sounds at her now, forfeiting all understandable language. The shrieks stabbed and rattled her mind, she wanted it to stop, she wanted it to end. Celestia felt her magic grip onto the cloud, and without a moment's hesitation she flung her head back. Her magic ripped the cloud from Sunset's horn, and flung it up and into the air. Celestia let go of Sunset for the moment, and focused on the entity. She scowled as she looked at the wriggling thing, it's dark, shapeless form writhing in the grip of her magic.
From the base of her horn, Celestia lit a spell that would terminate the thing. The pure magic swelled from the base, and shot its way through her horn, blasting into the cloud, and dissolving it in a bath of pure, bright light. Once not an ounce of the cloud could be seen, Celestia drew her attention back to Sunset. The Unicorn lay crumpled on the ground at Celestia's hooves, her head pressed against the floor. Celestia could see from the way her shoulders shuddered, that she was sobbing intensely.
The Alicorn leaned down slowly, and rested on the floor beside Sunset, drawing her legs in and spreading her wings across the floor around her. Gently, she lifted one wing, and brushed Sunset's back. Sunset shot her head up and looked at her mentor, tears staining her cheeks and pinning her coat to her face. Her large turquoise eyes pleaded with Celestia as she looked at her. Celestia felt her heart break slightly as she saw her student's expression, so much fear and deep sadness.
"I- I'm sorry!" Sunset's voice cracked as she finally spoke. Her head fell to the floor once more, and her eyes clamped shut. "I'm sorry, I'm sorry!" Her breathe shuddered as she pleaded, letting herself sob intensely. "Please- please forgive me your majesty! I didn't know what I was doing..." She heaved more tears with her final words, the floor drowning in a small puddle under her face. Celestia let her own emotions take over for the moment, tears peeking their way out of her eyes as she replied.
"Sunset..." She spoke, looking down at her student with such care and worry. "It's alright, you're okay. It will BE okay. I forgive you." Sunset opened her eyes once more, looking up at Celestia with worry and confusion. "I... was going to do something bad." Sunset said. Celestia blinked and nodded.
"I know, but it wouldn't have been you who was in control." Before Sunset could reply, Celestia continued her explanations, looking around the room of dark magic as she did so. "It tells you things, things you want to hear, or might even believe. It draws you in, makes you promises. And, when it's done enough, when it has you fully in it's grasp, it takes you over. You're still in there, somewhat, and you can see everything. But it makes you do things... things you might not've done otherwise."
More tears peeked their way through as Celestia spoke, falling daintily down her face. Sunset noticed this, and felt more pained, realizing how much trouble she'd caused her teacher, mentor... her friend. Sunset lifted her head, and pulled her hooves in close to her body, suddenly feeling inadequate to be so close to Celestia. "But I do not blame you, Sunset Shimmer." Celestia drew her attention away from the objects in the room, and back to her student. Celestia lifted a hoof delicately to Sunset's face, lifting the Unicorn's chin to meet her own.
"I made a promise to teach and guide you... but I clearly have not done enough to keep you safe. For that, I am sorry Sunset. I never wish for you to feel as though you are not enough, or that I do not value you." Celestia lowered her hoof, and began to rise. Sunset hesitatingly rose with her. "No-one can replace you, my student." A sudden thought occurred to Celestia and she gestured for Sunset to walk with her. "There is something that I should tell you... that I should have told you long ago."
Celestia walked out of the room, Sunset quickly following after her. Celestia looked back at the door, shut it and quickly put a binding spell on it, so that no-one else would be tempted by those dark spells. The Queen walked down the halls of the castle, and finally into the throne room, Sunset Shimmer following closely behind. Celestia stopped in the middle of the room, quietly observing the sunlight, as it cast its light into the stained glass murals in the halls, bouncing brilliant colors across the room.
Celestia turned to face Sunset, and breathed in a small sigh. Her student stood before her, her head hung low in fear and shame. "Sunset... I am sure that as a foal you were told the tale of the Mare in the Moon?" Celestia asked. Sunset's head pricked up in surprise at this, looking at Celestia inquisitively.
"Yes... My father would read it to me and my brother before bed." She wasn't sure why Celestia was asking about a foals tale, considering all that had just happened, a bedtime story didn't seem to be all that important.
Celestia looked out at the sun as she spoke, her horn lighting with magic as she began lowering the sun. "The tale it speaks of, is more than true. My younger sister... Princess Luna, fell to the call of the dark magic. It saw the pain in her heart, and festered in it. I was forced to banish her, and I have ruled the day and night in her absence." The sun vanished behind the horizon, and in the opposite section of the sky, rose the pale glowing moon, clearly plastered on its surface the silhouette of a mare's head.
Sunset watched as the moon crept its way into the night sky, the deep blue being speckled with dots of tiny stars. "I lost my sister to the dark magics... I do not wish to lose anyone else so close to me to its clutches again." Sunset gulped, the guilt of her almost taken actions still holding a tight grip on her psyche.
"Your highness... why are you telling me this?" Celestia's magical grip vanished from her horn, and she took a few steps closer to Sunset.
"It may seem wrong for me to say..." Celestia breathed in quietly, "But I... do not wish to be alone anymore. It was hard for me, ruling without my sister all those years." Celestia's gaze softened as she spoke.
"It will not be long until Nightmare Moon... my sister, is freed from her prison. I do not have long left until I have to confront her once more, until she wishes to fight with me again." Celestia looked intently into Sunset's eyes. "I wish for you to stay my student Sunset Shimmer. And... I ask that you assist me when the time comes that Nightmare Moon is freed. I do not have the same power I did before, the Elements have been lost to me for some time."
Sunset nodded in understanding. "And... if you can't defeat her, she will have enough power to take over, wouldn't she?" Sunset croaked, unsure if it was her place to state what she did.
Celestia nodded. "Do you accept, Sunset? I will not force you to stay in the Castle if you do not wish to do so. You may return home if you like. But I do not hate you, and I wish that as your teacher, that I can guide you and protect you, the way I promised from the start." Sunset's eyes traveled down to the deep red velvet carpet the two stood on.
Averting her eyes from Celestia gave her the briefest moment to asses her options. She believed her mentor, that she did not hate her, despite all that Sunset had done, and was about to do. But she could never make up for her wrong-doings against Celestia if she left the Castle and returned home to Sires Hollow. If she stayed her student, perhaps... just maybe over time she could makeup for all that she had done, and gain Celestia's trust once more.
Finally, Sunset returned her gaze to Celestia, nodding her head as she gave her answer. "Yes, your highness. I will stay your student." Sunset gave a bow, leaning her head down far enough to point the tip of her horn to the floor. "I promise to makeup for all that I have done, and earn your favor once more. I will be faithful, loyal and hard-working, your majesty."
As she rose she saw a warm smile spread across Celestia's face. "There is no need for all that, Sunset." She chuckled.
Sunset gave a sheepish smile, but shook her head. "I know, but please, let me agree to those terms your majesty. I have wronged you, even if I didn't do anything... I was planning on it. I have to make it right... at least in my mind I do." Celestia's wing gently brushed Sunsets shoulder.
"Well," Celestia spoke, "Alright then. I agree to your terms as well, Sunset Shimmer." Celestia began walking towards the large doors of the throne room. "But for now, let us both get some rest... it has been a long day. We will have much to do in the morning, but for now we both need a goodnight's sleep."
Sunset nodded in agreement, suddenly realizing how exhausted the whole ordeal had left her. There was much she needed to do, to makeup for the wrong that she had almost done... Sunset wasn't entirely sure what she would do to makeup for it... but she was sure that whatever was in store, she would stand by her Queen's side, no matter what.