Celestia rose from her bed after another sleepless night. She'd been kept awake by a never ending torrent of fears and anxieties that swirled around in her mind like a swarm of starving Parasprites. It had been a mere three days since her beloved sister Luna had taken up the new name of Nightmare Moon and attempted to usher in an eternal night. Though brief, the battle between the two had been so intense that from Celestia's perspective, it seemed as though it had lasted for years, a notion that was supported by the utter devastation caused to their old home, the Castle of the Two Sisters. After it was all said and done, Celestia had no choice but to banish Nightmare Moon to the moon itself, an act that while painful, seemed to be the only way to safeguard Equestria.
In the aftermath of battle, she struggled to understand just what had happened. Luna transformed into something else, something sinister before attacking with vicious abandon, but for what reason? It's possible that Nightmare Moon had said it at some point during the battle, but in the heat of the moment, Celestia was far more focused on protecting herself, so she would never be able to remember. Whatever the reason, the outcome was obvious, Celestia had been forced to seal her sister, her own beloved little sister away within the moon likely never to return. She'd been forced to fight against family, and that act created a greater wound in the Princess' heart than she even thought possible.
Looking past the emotional pain of betrayal, Celestia knew full well that she faced a seemingly impossible task. With Luna gone, she would have to rule over the vast country of Equestria alone, raising both the sun and moon while also trying to keep order in a land that was still suffering from the shock of losing a princess. While it was true that most of the day to day issues were managed by the mayors, governors, and other officials, the fact still remained that any and all pressing issues would fall to her and her alone, something which daunted her more than anything else. The next time that a major crisis arose like Discord's arrival or an invasion by the Griffons, would she be able to handle things without her sister's help? The Alicorn doubted it, and that sent shivers down her spine.
Leaving her quarters and walking down the still unfamiliar hallways of Canterlot Castle, the princess made her way to the balcony, so that she could raise the sun and usher in yet another day for the citizens of Equestria. After completing her sacred task, a single idea overtook her, she would have to seek answers or at the very least, closure. Determined, she made arrangements with her assistants so that they could keep things stable while she was away before heading out to her now abandoned home. She honestly didn't know what she would find there, but she had a feeling that whatever it was, it would help her get it together.
After an hour's trip, Celestia arrived at the Castle of the Two Sisters. Upon arriving, the full impact of what she had done finally hit her. The castle was once the pride of Equestrian architecture, standing tall against the surrounding landscape, but now, it was little more than a crumbling ruin. Such was the intensity of their battle, that after only three days, the former capital looked more like the fortresses of the ancient Pony Tribes than a work of modern architecture. Above everything else though, Celestia knew that this castle had been not only her home, but Luna's home, and the fact that they were so eager to utterly destroy the structure was almost as sad as the battle itself. The Alicorn princess shed a single tear in regret before standing tall once again and heading into the ruins.
Though most of the structure had been absolutely devastated, there were still areas that resembled their former glory. When she looked at each of those areas, she saw scenes of her past replay in her mind. Long summer days spent playing hide and seek, cold winter nights curled up near the main fireplace, and rainy evenings sent admiring the clouds as they swept over the land were just a few of the memories that this place held. In all of these memories, she knew that Luna was with her and that now, she'd never be able to experience any of those good times ever again. Just as how she had banished her sister, nature would soon remove this structure from Equestria, consuming the cold stone with new growths of plant life. Considering the circumstances, Celestia believed that allowing nature to seize that castle was probably for the best.
As she walked through the ruins, her hoof bumped into something, and when she looked down to see what it was, she was surprised to see the unmistakable binding of one of her magic tutor's old spell books. As she picked it up with her magic, she shuttered at the sight of the tome's cover. Embedded into the innocent looking brown leather of the book, there was an emblem in the shape of a galaxy which seemed to shimmer with all the colors of the night sky. This was the one tome that she and her sister weren't allowed to read, Celestia never knew why, but it was always stressed that this book was forbidden. She looked at it for what felt like an eternity, before one fateful idea entered into her head, maybe the book would have someway of saving Luna. The idea seemed preposterous, there's no way that some “remove Nightmare Moon and bring back Luna” miracle spell would just exist in some random forbidden tome, and yet, she couldn't help but shake the idea. After much internal debate, she decided to open it, just to take a peek, if she didn't see anything promising right away, she'd close it immediately and never even think about opening it ever again.
Celestia slowed opened up the aged tome, only for the pages to turn out of her control before settling on a page, that wasn't so much a page as it was a hole. Unable to look away, the Princess gazed deep into the sprawling tunnel of flashing green lights that stood before her, stretching on farther than she could possible see. She only got a few minutes to stare at the anomaly however, as she soon felt herself being pulled into the tunnel by an impossibly strong force. As she was somehow thrust into the open book, she felt herself flying through the tunnel at extreme speed before her vision was consumed by a bright flash of white light and her vision went dark.