Time.
Time loses meaning when you don't have much a use of it. Sometimes, losing track of time is good. You can lose track of time doing something enjoyable, spending time with a friend, or forgetting time even exists when with a lover. But even during these activities, time comes back to you. It may not be the center of one's attention, but it is still there sooner or later. Even if you can't see it, like the wind, it never goes away.
Luna wondered, briefly, how long it had been.
After her failed coupe against her sister Celestia, Luna had been banished to the very moon she held control over. She became a prisoner to her domain, sealed away where she never thought she could be, and helpless to escape. That didn't deter her from trying, and for a long time, too. Hope was a persistent emotion, one that could get one out of bed or topple countries. She tried anything and everything she could think of, from flight to spells to everything in between. But the magic that grounded her or defeated her spells time and time again was simply too powerful, even for an alicorn such as herself. Even her far more powerful other half couldn't so much as strain the barrier around her impromptu prison.
When she was first banished, Nightmare Moon threw all she had at the prospect of escape. She never slept during her trials, and would only do so because she passed out from exhaustion. When she didn't have the strength to fly, she would use spells in a futile attempt over and over. Once her formidable magical capabilities were drained, she went back to flying. She would repeat that useless cycle until her body gave out. When she awoke, she would begin again with the same vigor as before.
Eventually, she changed back to her princess self. Wither this happened days, weeks, or years after her first day alone on this lifeless rock, her crowning jewel in her majestic nighttime sky, she didn't know. All she knew was that she was alone, with her other half too spent to resist her attempts to reclaim her mind. It hurt. Not in a psychical sense, but an emotional one. Her heart ached that her beloved sister would take such a drastic measure to ensure that Nightmare Moon would fail and ultimately be defeated. Her eyes stung from the endless time she cried on the moon, until there was nothing left to cry about. Her sister had to make sure that their kingdom would be safe, and Luna had to pay the ultimate price for it.
After the sadness passed, Luna felt shame. She felt an overwhelming feeling of it. How could she? How could she be so childish? How could she put her kingdom in such despair for her own selfish want? The worst of it, how could she ever think of bringing harm to her sister to do so? She felt terrible for her decisions, her weakness to herself. She gave into her hate, her jealousy, her desire for power, and she kicked herself every day for it.
Day... How could she define day in a place where the sun neither raised nor set on? She knew what day was back in Equestria... that little blue orb high in the sky. It seemed so close, like she could reach up and touch it with her hoof, but she couldn't. When she flew to it to try and escape this hell, it only seemed to shrink away, as though it feared her return. Most of the ponies in Equestria most likely did fear her return. Or rather, the return of Nightmare Moon.
After the shame, came anger. Blinding anger at her sister that she would have the audacity to banish the rightful ruler of Equestria! Equestria was her kingdom! If the ponies would so happily worship her sister and shun her beautiful night sky with their insulting sleep, then she would take what was rightfully hers! When she returned, she would banish her sister to this place! This was an outrage! The Princess of the Night will not be some lowly prisoner on her own jewel! When she returns, she will wreak havoc upon her sister, and destroy those damned Elements of Harmony!
"Yes! Yes! Let me take control! Release me from this cell inside your mind, and together, we shall rule all of Equestria!"
Luna's rage dissipated at that horrid, cackling voice that plagued her mind. "No. No! I will not harm my sister! I am better than you!" Luna shouted into the empty space around her.
"Are you? Even after you released me the first time to overthrow that wretched mare? The 'harm' that you allowed to come to her without question, or even so much as lifting a hoof?"
Luna swallowed back tears, "I had no intent of harming her! I thought that if I was to intimidate her, she would accept my conditions! You harmed her!"
"Yes, I did! Because I *am** you, as you are me! We share the same mind, the same body, the same desires! We should rule Equestria! Our night should shine over their little heads! We are one and the same!"*
"You are wrong! We could never be more different, you evil mare!" Tears couldn't be stopped.
"Oh, but I am right! And you know it, too. Deep down, in the very depths of your being, you know that I am a part of you as much as you are a part of me! We have never been separate, dear Luna; only blind to one another."
"And it was better when I was blind to you! I love Tia, and she loves me!" Her strength was failing. Her argument was weak. And she knew it.
"If she loves you, then wouldn't she die for you? If that is the case, it seems she does not love you as much as you think, Luna. Why would she make her innocent little sister take the fall for this when she easily could have locked me away, like you've done for so long? Could the Elements not have simply erased me from your mind?"
"... They... they could have..." Her voice was only above a whisper.
"Then why didn't she? What was stopping her? Her voice sounded of victory.
"..." Luna had no answer to that. At least, not one she wanted to admit.
"Exactly. To erase me, would mean to erase you as well. Because I am not just some form of corruption, some taint that can be undone, but I am a part of you, I *am** you!"*
"No... No, you can't be!" Her voice was weak, her legs gave out and she fell with a dull thud to the gray dust.
"How blind will you be to the truth?! How long will it take for you to realize that you are wrong?! If I am not you, how am I in your very mind, producing thoughts inside your own head?! Why would I desire exactly the same thing that you desire?!"
"What... what should we do?" Luna asked. She was broken, defeated, and worst of all, wrong.
She could sense the smirk in her head. "I am sorry I had to be so hard on you. On *us. But there was no other option. As for what we should do, I must rest. **We must rest. It will take all of our strength to align the stars correctly to overpower the barrier that has been placed around our moon. Without the help of our starry sky, we will be powerless to escape. But with it..."*
Luna rose. She starred intently at the small ball that was Equestria so far away. She stared at the small land that was hers. Her anger was back. That wasn't just Equestria, it was her Equestria. And she will take it. No matter who stands in her way.
"... We will have our rightful revenge on your sister. We will claim our throne from her tyrannical grasp. And, we will cast our glorious stars over the land, for all to enjoy and worship, just as they worship her lone, pitiful star!"
"You are right. Equestria will be ours!"
And so she waited. This escape plan would take quite a bit of time. But she has all the time she needs. So she must wait.
And wait.
And wait.
For in the end, it all be worth it, and even time itself will bend to her will.
