Author's Notes:

Get some tissues.

When they were first banished, Nightmare Moon almost didn't hear Luna's screams of loneliness and despair over her own of rage and indignation. To have come so close to bringing an eternity of night to a land populated by easily-spooked creatures, only to be denied complete victory in large part because her host was so stubbornly unwilling to kill her elder sister for it was maddening. Even worse were those thrice-cursed Elements of Harmony! Where in that forsaken little plot of soil had those even come from? The Princess who she'd held captive had never once mentioned or even thought of them during her entire time on the moon as an invading force. On that note...

"BE SILENT, YOU SNIVELING WRETCH!" Nightmare Moon raged at the wailing voice inside her head. It was incomprehensibly annoying to only be able to hear one voice screaming. Worse was that the owner of said voice was completely helpless inside her, so there was really no sport in it.

"Were it not for you and your abomination of a sister, I could have ruled a Night Eternal! I could have held all of your pathetic little subjects in abject terror until they finally succumbed to the frigid and barren world the land would have become without that cursed sun! Equestria would have become just as the Moon is, only with more space upon which to raise tributes to MY GLORY!"

However, it was only a matter of time until Nightmare Moon discovered that her banishment also restricted her from being able to access the greater majority of the Realm of Dreams, where the true depth of her race's power and capacity to influence the pony races -to instill and nurture the fear which the Nightmares fed off of.

So she resigned herself to make the most of what she had. And what Nightmare Moon had was the very young immortal Princess Luna, full of bitterness and envy, fear and self-loathing, loneliness and now despair. In order to stave off the boredom that an imprisonment with only one source of entertainment would induce, the Queen of Nightmares decided to take some time to influence each of Luna's negative emotions individually. This plan, of course, was significantly hindered by Nightmare Moon's inability to reach the Equestrian artifact that allowed it user to see other worlds. One in particular of which bore horrors the little ponies could hardly begin to fathom, and which she often found herself turning to for creative inspiration. There was such a wide array of marvelously horrible things the bizarre two-legged creatures of that world did to each other, and even themselves, that she believed that she could try a different one every day for the next thousand years and still run out of time before she ran out of methods of torture.

Alas, however, such luck was not on her side, which meant that she was going to have to be creative. Well, there was nothing wrong with being creative now and then. It helped the time slip by, and Void knew, Nightmare Moon certainly needed that. Still facing the land she had nearly claimed for her own, she sat and closed her eyes, drawing her consciousness inward so that she could focus on her captive, and so they could converse 'face to face'. In her mind's eye, she saw the phantasmal cage within which the Princess of the Night was bound. Illusory chains bound all four of her hooves and could be moved about the cage as Nightmare Moon wished. From Luna's perspective, however, the chains and cage were real. The only input she ever got from the living world were what Nightmare Moon allowed her to see and hear of what Nightmare Moon herself was looking at and listening to while using Luna's body.

The Nightmare transformed into a cloud and flowed into the cage, then reconstituted herself wrapped around Luna from behind. Reflexively, Luna thrashed and tried to fight her off, even knowing that she could not win. Nightmare Moon just pinned her down and waited for her to give up. It took longer than expected, but the villain didn't mind. Passing the time was what she was here for, anyway. As the princess's struggles subsided, Nightmare Moon leaned over Luna's shoulder and pressed their nearer cheeks against one another, taking a moment to enjoy Luna's shudder of revulsion before revealing her plans for how the two of them were going to spend their time banished on the moon together.

"I know that you already know that I will make you suffer..." Nightmare Moon jeered to Luna in sotto voce, as though there were any reason to treat this conversation within their semi-shared mind as an especially intimate one. For Luna, it only boosted the sense of violation that being so embraced by this monster who had stolen her very body instilled in her. Worse yet, she knew full well, was that the agony of her imprisonment alone here upon the moon was only just beginning. "What you might not know, however, is exactly what your torment will entail! Which I am quite glad for! I do so love surprises! HAHA HAHAAA!"

"D..do thy worst, vermin! Thou canst not break me!" Luna tried to puff herself up to show her pride and her faith in herself, but the sickening encompassing presence of her assailant made every movement instill in her the urge to vomit.

Nightmare Moon seemed to only be letting her move to a standing or sitting position just to push her down again. Refusing to play her tormentor's games, Luna petulantly flopped onto the unforgiving floor of her imaginary cage. This proved to be a mistake, for as soon as she did, she felt Nightmare Moon pushing herself into Luna's compartmentalized consciousness, causing her mind to reel at the prospect of being forcefully invaded twice over. But it was too late to stop her now, so Luna resolved herself to simply bear it until Nightmare Moon either finished with her or was interrupted by some highly unlikely external factor. After an unknown time, the darkness fled her vision and she found herself at the edge of a sea, or possibly a sky, full of endless gray. The two of them were separate entities once again, at least within the limits of Luna's perception, and she didn't even want to think about that right now.

"Haha! You wish I would do my worst to you! Do you take me for a fool? ...don't answer that. I will NOT grant you the reprieve of slipping into insanity or dying of fright, my little pony! You will know hope! You will know love! You will know dreams! And ALL of those will be shattered before you! Every day for a year, you will live the life of one of the soldiers you brought with you to invade my homeland! Every night, you will die his or her death! After a year passes, we will move on to another soldier! And so on and so forth, until I tire of it, so perhaps a thousand years or- oh! Oh oh oh!" Nightmare Moon's monologue was cut off, and she grabbed Luna's chin and forced her to look her in the eyes. "Oh I so love it when you cry silently! You do it so beautifully, I must keep such an occurrence rare so that I may relish every moment of it!"

"S-stop it! Why must thou do this to us?" Luna's ears lowered and she leaned back and away from Nightmare Moon, who responded by leaning in and licking her tears off her cheeks with audible gusto. The action sent shocking waves of that terrible sense of wrongness that being pinned by her before had caused.

"Do not ask questions to which you already know the answer, dear filly. It really is beneath you. Just so you know, if you discredit yourself as my consolation prize, I will have to take the price for that out of somepony's mind as well. And in case you haven't noticed, you are the only pony here. Anyway, I am quite excited about this little project, so let's begin immediately, shall we?"

Before Luna could respond, everything went black.

* * *

Princess Luna awoke in the latest of a number of times she had long since lost track of. It was always the same when she woke up: she was lying on her back, staring up and the eternally gray sky that dominated the world where Nightmare Moon first proposed this manner of suffering for her. How long had she been enduring this now? A century, perhaps? Two? How many ponies had she lived and died as? She had long since lost track of those, too, but somehow got the impression that Nightmare Moon wasn't sticking to the rules of her own game. Then again, it was not as though she had a reason to, since she was the only player, whereas Luna herself was a mere piece.

Something was different about this time, however. The burdens that had restrained her in the depths of her mind seemed lighter, somehow. Almost nonexistent. Seizing the opportunity, Luna concentrated and burst through the Nightmare's grip. For a few precious minutes, Luna could see Equestria directly, with her own eyes. However, something passing just under her initial field of view drew her attention downward, and what she saw moved her heart. The stars which she had assigned to the ponies who had served her in the Lunar Invasion were racing across the sky as they had when she first did so as a tribute to their sacrifice. It seemed that each of her soldiers' souls, as well as those of many other ponies who had died in the intervening time, had bound themselves to these stars and were now trying to use them to reach her. Each one, however, only had a moment to try, inevitably failed, and continued racing along in accordance with some arcane rules she could not begin to comprehend. A faint hum perked up her ears, and she leaned as far forward as she could manage, thus discovering that the hum was actually a song.

"Do not worry, Filly Princess..." the shooting stars sang to her. "Do not let your heart drown in tears. We will save you, Lunar Princess. Even if it takes us a thousand years."

Now openly crying, Luna reached for the shooting stars, straining herself until she lost her balance and fell onto the surface of the moon, kicking up a cloud of moon dust in the process. She tried to flap her wings, but to no avail. They were paralyzed by the Elements when they banished her. She tried to stand again, but her legs refused to obey. Looking down, she watched in horror as the dust cleared and revealed that her coat was black once again -or perhaps, still- and by extension that she was still a prisoner in her own body. Starting at the back of her mind and moving forward, accompanied by that familiar sickening feeling of violation, was the laugh of her hated enemy as Nightmare Moon swept up to fully reclaim Luna.

"Gotcha!" Nightmare Moon giggled, and Luna knew that her respite was over and in fact, had only occurred to prolong the Nightmare's delight in chipping away at her sanity. "Good news, Princess! Only nine hundred and ninety years remain!"

* * *

Back on the surface of Equestria, Celestia spent the evening preceding the Winter Night, the longest night of the year, in the same place where she had spent every one prior to that. Indeed, for the first ten years after she was forced to banish her precious little sister, it was where she had spent every evening: at the zenith of the tallest mountain in Equestria, in the hopes that Luna might see her and understand that Celestia still loved her. However, upon seeing the display put on by the shooting stars, and learning of their meaning from a unicorn scholar who specialized in the field, Celestia spent less time grieving and more time being proactive about Luna's situation. Namely in obscuring the relationship between Luna and Nightmare Moon, to reduce the possibility of her pony subjects fearing and hating Luna if -when she was freed from her imprisonment and returned home.

Still, as one year after another passed and progress in saving her sister seemed slow to the point of being virtually nonexistent, Celestia took it upon herself to return to this place to allow herself to cry where nopony might see or hear her. She cried tremendously every time this night rolled around, because she would not be able to escape spending the whole night staring at the moon and seeing the shape that meant her sister was still imprisoned on it. Since she was on a mountain, more often than not the frigid, biting wind would sweep her tears right off her face and scatter them across the sky. Celestia chose to believe (correctly) that nopony who saw them would be able to identify them for what they were, let alone trace them back to her.

* * *

Nearly a thousand years after Nightmare Moon's imprisonment, long after the vast majority of ponies forgot she actually existed, a pretty foal with a deep red and bright orange fiery color pattern was born. Her mother decided to name her after the most beautiful thing she had ever seen: a mysterious shimmer at sunset, which appeared across the sky near the great mountains every year during the evening prior to the longest night of winter.