The moon wasn’t a very exciting place. It didn’t take a smart pony to figure out that much.
Or an alicorn princess, for that matter.
When she had first arrived, Luna ticked off the days with scratches on the walls of her palace, made with shards of glassy moon rock, the castle entirely void of any other life than her own. Her daily ritual went on for months. After a while, the wall was filled with tiny tally marks, and so she moved on to the next one. And the next.
It got to a point where she just decided to stop counting altogether. Acknowledging her own time spent there felt more and more painful with every day that passed. But despite the countless days spent on the barren rock, she could never say she was truly alone…
No matter how long she spent unconscious, she could always feel it nagging at the edge of her mind, the immense pressure of pure darkness always there to remind her of what she’d done. Always observing. Waiting for any opening of weakness, to strike with vicious precision, and shatter her mind like it’d done so many times in the past. It was unlike the Tantabus; that creature was her own personal nightmare, her creation, but it only resided in the land of dreams. It couldn’t get to her in her waking hours.
Nightmare Moon, on the other hoof, could come haunt her at any time.
She could feel the pressure there again, right in the center of her chest, squeezing at her ribcage beneath her polished obsidian breastplate.
The discomfort made her shift her hooves where she sat, but she tensed herself to stay still. She wanted to enjoy the fleeting feelings of stillness, in both the starry black skies and her own mind.
Her draw in of breath was cut short by another sharp pressure pushing down on her chest- no, pushing out.
As Luna struggled to her hooves, her mane’s seemingly endless galaxies fading away to a faint glow, she flared out her wings behind her and steeled herself. She was ready for it this time.
Letting out another deep breath, she concentrated on the pushing and prodding inside of her, and willed her body to let it free.
Immediately, a wave of agony wracked her body as a metal-clad hoof was pushed through and out the plate of her chest, the rivulets of dark magic flowing out around it like ichor from an open wound. As she shook in place, wings flapping erratically to stay upright, the form of another entire pony stretched it’s gruesome form from out of her own, a deep galaxy-strewn mane followed by horn and pair of midnight blue wings. When the last wisps of its tail finally moved outwards from her chest, Luna collapsed, gasping for breath as the newcomer bubbled in its pool of pure shadow.
Looking up, she was met with two piercing, slitted eyes, and a mouth full of razor sharp teeth. Nightmare Moon stretched her wings out lazily, her horn lighting up as she levitated something into Luna’s view. Her hazy vision could just barely make out that it was… a teacup. The creature’s voice was just as dark as the magics it’d came from. A voice that was all too familiar.
“Care for some tea?”
Both their manes flowed silently, even without any wind to ever disturb them.
Luna looked somewhere in the distance, expression pulled tight as she tried not to look at her visitor. Her hooves were resting on the edge of their ‘quite lovely tea table’, made of blemishless onyx, resting tersely as Nightmare Moon sat on the other side.
Nightmare was keeping its gaze locked on Luna, a teacup held in the aura of its magic. Taking a loud sip (while the tea was still burning hot), it let out a hearty chuckle. Luna didn’t laugh, or even smile, her own tea sitting untouched.
“What’s wrong, Lu-Lu? You were so much more enthusiastic about my arrival the first time I came.”
She snarled at the use of her nickname, the nickname only one pony was allowed to use. A part of her didn’t want to give it the satisfaction of her anger, but she knew that would only make things worse for her later.
“...I am not going to break, you monster. There is nopony else who can get hurt, nopony that -”
“Oh, but there is, isn’t there?” It raised a hoof and poked her in the center of her chest, right where it had entered from. “You may think that it’s alllll over now, that since you’re away from your little ponies -” It spat out the word with ferocity, “- you won’t just be a nightmare.”
“But, oh; I know better. I don’t need to use your loved ones against you anymore.” It got up and started pacing around the petite table they were sat at, slowly drawing closer to Luna. “All I need… is time. And we’ve got all the time in the world to spare.” It said those last words mere inches away from Luna’s face, which then twisted with rage, before she lit up her horn teleported away in a flash of blue light. Nightmare Moon cackled to the sky, her own horn lighting up as she quickly traced Luna’s powerful magic trail.
“You can’t run from me forever.”
A flash of deep azure lit up the table below, as Nightmare teleported away.
Two teacups were left sitting, still steaming hot with nopony to enjoy them.
Luna didn’t want to stop running.
It felt cowardly, to a part of her, to always be running from her own demons. But for now, it was all she could do.
Hooves hitting rock brought up dust in plumes, nothing in Luna’s path as she galloped away from -
A flash of blue right in front of her eyes, and Nightmare Moon headed her face-on, still bearing a wide grin. With a yelp, Luna collided with it, the both of them falling over in a tangle of hooves and mane. With her eyes shut tight, she struggled against Nightmare’s weight, thrusting her horn upward as she tried to hit her off.
Her horn sunk deep into flesh with a sickening sound.
Luna ripped her head to the side, feeling flesh rip from bone as she took Nightmare Moon’s throat with it.
Getting to her hooves warily, she shook her head as blood dripped down her muzzle from her horn. Nightmare Moon had been staggered to the side, heavy breaths gurgling as the wound in her neck continued to gush blood.
It took awhile for Luna to realize that it was laughing.
Bringing its head up, a pool of dark magic formed around her torn jugular, dissipating to reveal its now-unscarred, jet black mane.
“Playing dirty, Luna? You know that won’t work with me.”
Standing still, shocked, Luna glanced upwards as the viscera on her horn evaporated into a thick black smoke, flowing back toward Nightmare’s body and coalescing at the tip of her own horn. The smile it had worn was now gone, its eyes now filled with an eerie white light. The galaxies in its mane seemed to grow ever-larger as it stalked closer.
“I know you’re afraid of me, Luna. I know everything about you. And I know… you won’t be able to escape this.”
Luna’s legs were shaking. Why were they shaking? “I’m not- I’m not afraid of you, monster! You will never -”
“Never break you?” It laughed, all traces of playfulness gone from its voice. “Oh, Luna. I don’t care how strong your will is.”
“You thought you were strong before, and yet; I still beat you.”
Darkness encroached around the two of them, Luna’s legs refusing to move as a paralyzing fear gripped her very being.
“You thought, if you could just fight me off, we could live - together -”
Nightmare Moon stopped, leaning down to whisper mere inches from Luna’s face.
“When I’m done with you, there will be no Luna left to live with.”
Faster than she could process, Luna felt all of its dark energy rush into her chest as it plunged a hoof back into her, screaming out in agony as pure evil thrummed through her veins. Her eyes flashed out a blinding white, her whole being exploding with power as the creature entered her once more.
...And then, it was over.
Luna was left panting on the cold rock of the moon. There was no sound; no wind, no chatter, nothing. Only the sound of her own suffering.
The sound of a single tear trailing down her cheek, staining her dark fur, and the quiet plop as it hit the ground.
She cried.
For herself.
For Celestia, her dearest sister.
For her little ponies.
For the monster she was going to become.