900 years later

It was going to happen any day now, and Nightmare Moon was ready to fight. She had the past 1000 years to prepare herself for when she returned to Equestria. She was ready to bring down the lying princess and bring truth to all. She was ready to make others adore her and her night. She was ready to bring the eternal darkness. She was ready to bring the truth to all ponykind. She was ready to avenge Wishing Heart, Aurora Skywriter, and a couple others she had seen while in her imprisonment. She was ready.

How dare Celestia lie! How dare she be so selfish! How dare she fool every pony and treat them like her personal puppets! How dare Celestia hurt her subjects without giving a hoof about them!

Nightmare Moon was ready to fight and save Equestria from Celestia and her lying light. But she needed to do something first. She needed to visit that oak tree, on that solitary hill, in Fillydelphia to see the letters Aurora Skywriter had written 900 years previously. Then she could destroy her sister!

She wanted to read them so bad. She hoped that when she was successful, she would be able to bring the truth to all ponies. So that they could see what Wishing Heart, Aurora Skywriter, and a few others had seen. She wanted to do so much. But she had a few promises and personal things she needed to attend to first when she got back to Equestria, before she started her take over.

It was time. She felt it. She saw the stars in the distance that had come to free their Princess at last. She closed her eyes, and felt a strange sensation go over and throughout her entire body, right down into her very existence. She felt a breeze. A breeze. It felt so wonderful to feel it blow through her mane, and ruffle her fur. She had not been able to enjoy this in the past millennia. She opened her eyes at last and gazed at the moon she was no longer trapped on, and a faint smile crossed over onto her face. But despite how wonderful this moment of freedom was, she needed to be somewhere. Then she could enjoy her freedom. And from there, she would start her conquest.

She took in her surroundings, and it looked like she was on the edge of the Everfree forest. She looked around a few more moments, then she teleported to Fillydelphia. She wound up in an abandoned alleyway, and in the distance she saw a hill with a big tree swaying in the wind. The hill. The tree. She almost couldn't contain her excitement as she once again teleported, but this time it was to the hill, the tree, and the letters.

When she got there, she was worried that someone might see her. But she then realized that from where she was standing, plus the surrounding areas, she was completely sheltered from view. She then used her magic to summon something that she could sense. That something was the letters that held truth and passion. A few seconds passed away and her magic latched on to what she had come for; a box rose up out of the ground.

Nightmare Moon took a few moments to observe the box's elaborate detail. The workmanship was exceedingly fine; the wood seemed to be made of the same oak as the tree that loomed overhead; carvings of bluebells under a night sky full of stars and a crescent moon decorated the box. She lifted the lid off, and the scent of lavender came up to her nose. And there, in the box, were the letters she had waited over 900 years to read. As she took the first one out, she was oh so careful. Even though Nightmare Moon's conscious mind knew that they had an eternity spell on them that protected them from all harm, her subconscious still worried that they were so delicate and fragile, that they could break apart at any moment into dust that would be lost forever. Before she unrolled the letter, she lifted it up to take a whiff. It smelled like old parchment, but it also had a faint and distant, yet still detectable, scent of lemon and peppermint.

She now began to unroll the yellowed aged letter, and began to read it to herself.

Dear Princess Luna,

My name is Aurora Skywriter, and I just want to tell you that I have always loved your night. The moon and stars; the mystery and wonders; all the grace and awe-inspiring beauty that you bring every single night. Celestia lies, and us from your night sky. She is evil.

I am writing this to let you know that you are the only true Princess. You tell the truth, care about others, and are amazing. Celestia, on the other hoof, is a lying, backstabbing, no good sun demon. Her Sun is also terrible as it can only blind and burn.

I am heartbroken that you were banished, and I would have loved eternal night. But alas, I fear that no other ponies know the truth, and they believe Celestia and her lies. I have tried to free you, but have failed. I can only hope that when you return, you are successful and every little filly and colt of the future will know the wonder and majesty of your night.

May the night last forever, and save us all. You are not a monster, but a hero. I can only hope that others can see that too. May you exceed every expectation, and be bathed in eternal glory forever.

Yours now and forever,

Aurora Skywriter.

Nightmare Moon was almost in tears, and this was just the first letter. She didn't know what to feel exactly, as this was so much, and yet not enough at once. Nightmare Moon knew that Aurora Skywriter was very old and not completely mentally stable when this was written, but it was still the best thing she had ever read. She spent the next hour reading and re-reading the rest of the letters that had been written; there were 12 in total. These gave Nightmare Moon the inspiration she needed to go beat Celestia. Well, she already wanted to eliminate Celestia because of her day alone, but this just insured it. And so it was. No backing down, as it was go time.

She cast a restoration spell on the letters so they were as fresh as the day they were written, and to keep them that way. She neatly folded the letters, put them back into the box, and safely tucked the box back into the ground, and she also cast a spell preserving this place for eternity, and no other spell of any sort, even the Elements of Harmony couldn't undo it.

After she had done this, she teleported to the Castle of the Two Sisters, and she waited for her arch nemesis, her foe, her sister, Celestia. She was ready to destroy her sister, so where was she? Did she need to set the forest on fire to get Celestia's attention, so she could finish destroying her once and for all? Just as Nightmare Moon was going to move on and start her conquest, sister destroying or not, she looked into the sky and she saw Celestia at last. It was show time.

"You finally have the guts to finally show your lying face!" Nightmare Moon shouted at her sister.

"Sister, I do not want to fight you," Celestia replied. "This is wrong. Come back Luna, and be the little sister I knew all those years ago. This is my fault, and I know it. I admit I ignored, shunned, hurt, and forgot you. So much so that you felt that this was the only answer; to become this monster, but please come back Luna," Celestia cried out.

"I'm the monster?" Nightmare Moon said with absolute shock. "Me? No you are the only monster! And do you know why?"

"I know because of what I did which turned you like this, and that led us here," Celestia guessed, but she also had a hint of absolute certainty that this was the real reason behind all this.

"You are right when you say this is your fault, and that you are the reason I am like this. But that is just the beginning," Nightmare Moon said, just getting started. "What you did to me was one thing, and I could kill you alone for that. But there is so much more on why you are the real monster Celestia. I have just one example and there is probably a ton more that I shall fail to cover at this point in time this night. Do you even remember over a thousand years ago when you let a little filly's father just die? Do you even remember?" Nightmare Moon asked Celestia while she visibly shook with anger.

Celestia had no clue what Nightmare Moon was talking of, but whatever it was, whatever had happened, it clearly bothered her sister. But she honestly didn't know. "I am not sure of what you speak of. I am sure that I did not do such a horrible thing, but if I truly, truly did, I want to know everything," Celestia answered.

Nightmare Moon roared with fury. "Just because he couldn't pay his taxes you had an old fragile stallion thrown into prison. He was sick and needed help, which you denied even when he begged for it. You just didn't give a damn about him, and he died in your jail. And that was not even the worst part. He had a little girl with no wife as she had died as well, and she saw you take him away. She didn't even get to say goodbye to her father, and he died. She was left an orphan, but you didn't care. You left her homeless, alone, defenseless, hungry, and let her live a life in fear. She had no one because of you! And you don't even remember! How many others died because of you? How many little foals had to suffer? I fear I may never know, but I am here to avenge them all!" Nightmare Moon shouted at her sister.

Celestia was shocked to her core. She had not known about this. Had she really done this to her subjects? No, this had to be a lie to mess with her. "You lie," Celestia confronted Nightmare Moon. "You are trying to mess with my brain just long enough so you can distract me and bring eternal night as you seek revenge on something that happened over a millennia ago."

"This isn't about me anymore Celestia! This has absolutely nothing to do what you did to me anymore; this is about protecting my subjects from you, you evil tyrant! I don't care about eternal night anymore! I care about protecting those little ponies from you!" Nightmare Moon yelled at the Sun Princess.

Celestia hadn't expected that response. Nightmare Moon didn't care about eternal night anymore? How was that even possible? No. This had to be a trick, it had to be. But despite all her brain was telling her, she knew deep in her heart that what Nightmare Moon had said was true. She could slightly recall a face of an old, unfamiliar, but yet too familiar in a way, stallion. Was he the one who had died? That she had let die? Was she really the monster her sister claimed? But when she looked over to her sister, she knew without a doubt it was true. Her sister, now gone nightmare, was a physical manifestation to the testament of what she had done. She could try and fool herself that she had changed, but maybe she hadn't really.

But what would happen if Equestria knew what had happened for sure? Wouldn't they love her sister more than her from now on? She realized with a stab of guilt, she wasn't ready to give up her position in Equestria. She truly was selfish, but how to keep others from knowing all the little details? But, while she wanted to stay in power, she also really wanted her little sister back. The answer struck her like lightning, the Elements of Harmony. They could bring Luna back, and erase the awful memories that Nightmare Moon seemed to remember with frighteningly accurate details. And no one would need to remember and or know the terrible past. She felt awful wanting to do this, and she knew that she really had not changed, and she probably never would. Maybe one day, but that wasn't this day.

During the time it took for Celestia to think through all this and hesitate, Nightmare Moon was getting ready to fire an imprisonment spell. And when Celestia saw the firing beam, it was too late to run, block, react, or do anything for that matter. All Celestia knew after the painful beam had struck her was nothingness.

Nightmare Moon watched as her sister was sent to the Prison in the Sky in a blast.

The Prison in the Sky was a place that was neither space nor earth, but sort of in between. It seemed to be made of solid stone, but yet was as light as a cloud. Celestia would be in the Sky Prison trapped to the ground of it while she was held within a trance of her own mind, reliving all the awful things she had ever done in her long lifespan . It was a perfect prison, and it would hold her until Nightmare Moon could deal with Celestia further.

Nightmare Moon had conquered her sister, and now it was time for the rest of Equestria. She would be under the veil that she wanted to bring eternal night. But the truth would be revealed in due time, and until then, Nightmare Moon would have to be what the stories portrayed her as to get anywhere. But that didn't matter to her anymore. She had avenged Wishing Heart, and was about to make Aurora Skywriter's dream about to come true. One day all little foals would grow up with the truth, and they would never suffer.

But little did Nightmare Moon know, Celestia, even while still in her mental prison, had messed with the Elements of Harmony. She had them so that when used on her sister, they would revert her back and erase most of her memories. Equestria would never know the truth, just the story of a supposed monster, while not even realizing the whole story and who was truly behind it all. And Wishing Heart, Aurora Skywriter, and the others would be forgotten forever more. They would never be avenged, and their worst enemy would continue to prevail. A false god would continue to rule. All would never be well again.

Author's Note

So this is what I think happened before Nightmare Moon showed up in Ponyville in the first episode. Celestia is no innocent.

I think that Celestia might have messed with the Elements, and that is why Luna looked so different in the first episode. We see her with the star mane in the flashback in season 4, but not in season 1. But she regains her appearance by season two, but not all the memories that were lost.

Flashback

Season 1

Season 2