Over the Moon, Under the Weather
Celestia had prepared herself.
She had waited for this moment to come for 1000 years. Now that it was about to actually happen, it seemed almost unreal.
Once again, Celestia chided herself for her lackluster combat training – these last few centuries of peace had kept her too busy to exercise.
Not that she expected to win either way.
She knew that she did not have it in her heart to really do her sister harm – perhaps now this was even more true than it had been a thousand years ago.
No, she would engage her, keep her away from the nearby settlement – for a time.
She would be the distraction.
And when Luna – no, not Luna, not her dear sister – when the monster that had taken her body was confident in her victory, then...
Celestia felt a sharp tug on her horn.
Quickly, she closed her eyes, and concentrated on her magical senses.
There. A magical build-up, in the old castle. Just as she had suspected.
It didn't take much time to pin-point the exact spot. Right in the old throne-room. Celestia teleported.
She reached her destination before Nightmare Moon did.
Morbidly, she studied the steadily expanding ball of light, the electric arcs of blue and purple dancing on its surface...
Her horn was already lit with a spell. She would have the first strike, it seemed...
The crackle of magic grew into a cacophony. A barely defined silhouette, a shadow, became visible at the center, slowly gaining shape.
Celestia shifted into a charging stance.
The bubble burst. The dark, tall alicorn stared directly at Celestia.
Then she wordlessly collapsed to the ground.
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~~~
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Spike stared out the train-window, watching the landscape fly by – and trying to ignore Twilight's ramblings.
He failed.
“Come on, Twilight! Look!” He pointed out the window. “The sun's up, Princess Celestia is fine. There's no Nightmare Moon!”
“But Spike! The Princess would never cancel her appearance at the Summer Sun Celebration! She has never missed a single Summer Sun Celebration! Except...” Twilight's eyes somehow constricted even further. “Except for in 759 C.R., when Northern Yakyakistan joined forces with the centaur-mages of Kéntaura, and then they declared war, and Princess Celestia had to prevent the end of all Equestria!”
Spike found himself grasped in two purple forelegs, and violently shaken. “We could be at war, Spike! ...At war with Nightmare Moon!”
Spike glanced around, spotting a stallion clearly not reading his newspaper, a pegasus snickering behind a hoof, and a disapproving unicorn-mare shooting them a glare.
“Twilight...” He tugged on the panicking purple pony's foreleg. “Keep it down... You're making a scene!”
“Oh! Yes! Keep it quiet, keep it secret... We don't know if Nightmare Moon has infiltrated society! What if she has spies? Or screeing abilities? She could be watching us right now!”
“Twilight, how much sleep did you get last night?”
Spike was ignored.
“Did you get any sleep? At all?”
No response, just Twilight mumbling about Princess Celestia being in danger.
“...And weren't you up late the night before, too?”
Spike sighed, rolling his eyes.
“Well, you can ask her yourself when we reach Canterlot.”
At least talking to Princess Celestia would put an end to Twilight's latest bout of insanity.
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~~~
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Princess Celestia paced in her bedchambers.
Once again, she forced herself to look at her sister.
Her sister, who she had exiled to the moon for a thousand years.
Without food. Without water. Without companionship. Without anything.
And it showed.
Celestia averted her eyes once more. She couldn't. She just couldn't.
She felt disgusted with herself. She couldn't even bring herself to look at her sister!
Some part of her mind kept bringing up that Nightmare Moon had been a threat. That it all had been necessary to protect Equestria. That using the Elements had been the only way.
That little voice was drowned out by every beep of the heart monitor.
Celestia wiped her eyes with a foreleg.
An unfamiliar sound made the princess' ears twitch.
Celestia gasped. Luna's eyes were open. She was staring directly at her.
“Luna!” Celestia exclaimed. “Luna, I'm sor–“ Her breath caught in her throat.
The other alicorn's dry lips had parted, her mouth opened wide. Yet, the only sound audible was a faint wheeze, as if even the strength to speak was beyond her.
She didn't need to. Celestia could see it in her eyes.
Her eyes screamed silently – anguish, rage, and fear. Fear of her.
Celestia could see it all in the black alicorn's dragon-like slitted eyes.
It wasn't Luna. It was the Nightmare.
And Nightmare Moon was afraid.
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~~~
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Spike paced back and forth at the balcony, wringing his tail nervously.
Twilight had left about an hour ago, and then, that had been fine by him. She had rambled on about her silly “Nightmare Moon”-theories all day long, and Spike had welcomed the chance to read his comics in peace.
That was then, this was now.
Spike glanced down at the streets. Many ponies were still staring up at the moon, and murmuring – in confusion, mostly. He couldn't help but glance up himself, again, as he had done every other minute in the last half hour. If only Twilight would come back already!
There had been nothing unusual about the moon rise itself. It had been a little late, maybe, but Spike hadn't given it any thought at the time.
Twilight had run off to read some thousand year-old books. She'd insisted, that Celestia not receiving her was only more proof Nightmare Moon had returned, and was using a scheme “as devious as it was subtle”.
Spike had groaned. Against his better judgment, against previous experience, he had tried to talk Twilight out of it, take a breath and relax. Or even just read a different book, one that wouldn't mention legends of ancient vengeful goddesses.
But of course, Twilight had remained stubborn, and insisted on chasing down the literal Mare in the Moon.
Just half an hour ago, Spike had simply rolled his eyes at the thought.
Now, he wasn't so sure anymore.
Once again, Spike looked up at the moon. The empty, unfamiliar sight sent chills down the little baby-dragon's spines.
The Mare in the Moon – it had disappeared.
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~~~
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The next day, a small newspaper reached the kiosks roughly around sunrise. The kiosk-owners would spare it a glance, then sort it in at the very bottom, or at the edge to the fiction section.
That newspaper contained an article on page 7 that carried the following title:
“Nightmare Moon returns: Are your foals on her menu? 25 tips to make your foals taste bad (by L. Heartstrings)”
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~~~
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Princess Celestia's patience was at its end.
“What have you done to her?” Celestia barked, her fragile calm finally breaking.
The Nightmare flinched, just briefly. Then, she once again donned that infuriating smirk, though it didn't quite reach the eyes.
“Kept... alive,” Nightmare Moon croaked. “Kept... her... alive...”
Celestia reeled away from the bed, as if physically struck.
No. That couldn't possibly be true!
Celestia's mind was swimming in a haze, as a thousand years of pain and guilt were turned on their head, and then turned over again and again.
Nightmare Moon must've read her face, because she let lose a gurgle that could almost have been a laugh.
“Dead... host...” Nightmare Moon paused, to take a wheezing breath. “Usele–“ She was cut off by a series of heavy coughs, and without thinking, Celestia lunged forward to –
Celestia froze.
To do what?
To hold her hoof?
To tell her everything would be alright, to wrap her wings around her in a embrace, like she had done whenever her little sister was hurt?
To offer a glass of water?
To help the Nightmare?
No, she was acting foalish. That was still Luna's body, and her sister was still in there somewhere, even if the Nightmare was in control. She needed to heal Luna.
That meant giving Nightmare Moon that glass of water.
“I'm here for you, little sister,” Celestia whispered into Nightmare Moon's ear. Tears were flowing freely down Celestia's cheeks.
“Am... not...” The Nightmare rasped haltingly. Then she passed out.
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~~~
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Barely anypony had seen Celestia in days. Word was that nopony was to see the princess – she had canceled all court-hearings, and even a meeting with the Zebrican ambassador!
The ones who had seen Celestia claimed that she seemed... out of sorts, if such a thing was imaginable. And one staff-member had claimed that Celestia's mane had been pink, whatever one was supposed to make of that.
Even Twilight herself had been politely but firmly rebuked, time and time again. She'd stopped sending letters after the thought had occurred dragon-mail might have been compromised. Could that happen? Who knew what Nightmare Moon was capable of? She was an alicorn!
Twilight could not risk giving away sensitive information to the enemy!
Was she getting paranoid? Should she have gotten more than two hours of sleep in the last couple days? No, she didn't have time for things like sleep. She needed to save Equestria! She could sleep again when she'd saved Princess Celestia (and the world) from Nightmare Moon.
Besides, Nightmare Moon might be spying on her dreams. She could do that, or so some of the books said.
And so she hadn't sent a message telling her mentor that she was going back to Ponyville, to retrieve the Elements of Harmony – which, according to several helpful reference-guides in the Canterlot archives, were located in the nearby ancient Castle of the Royal Pony Sisters.
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~~~
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Finding the ancient Castle of the Royal Pony Sisters had been surprisingly easy. She'd expected Nightmare Moon to have set up traps, or some sort of magical golem as its guardian. The worst she'd encountered had been a broken bridge, and after some rather embarrassing sleep-deprived attempts to find another way across, she'd eventually remembered that she could simply teleport herself.
For hours, she'd tried as hard as she could, trying to create a spark using different types of magic at varying strengths and frequencies – but the sixth Element hadn't shown up. In the end, Twilight Sparkle had been forced to carry five heavy stones through a forest full of predators that came out at night. During nightfall.
In the end, she really couldn't say if it had been some doing of Nightmare Moon's, or simply bad luck that had led her into the middle of a pack of timber-wolves.
Or what had come after that.
The head of a chicken, the body of a snake.
She'd had enough time to recall the entry from “Handy Hooves' Guide To Equestrian Wildlife”.
A rough 5 – 15% chance the victim would remain conscious, varying depending on maturity of the specimen.
Not that she'd been able to do anything else.
It was dark. Dark, and cold. And she was alone. Very, very alone.
Twilight Sparkle really, really felt like crying, but the tears would not come.
After all, stone-statues could not cry.
-/-
In the absence of sight, Twilight's hearing had become much more focused.
Wind rustling through the leaves. An owl hooting in the distance. Another owl answering its call.
A rustle in the bushes – and the squeak of some unfortunate animal that may just have become someone else's dinner.
A few moments of silence.
More rustling in the bushes. The tiny scratching sound of a small animal scuttling past her. Then another. Birds flying away chirping in distress.
Something disturbing the wildlife.
Trees creaking, groaning. A prolonged cracking-sound, of a tree falling.
The heavy stomps of something large, coming closer. Closer, until it shook the ground.
Twilight braced herself. It was already dark – but closing imaginary eyelids helped.
She only had the hope that whatever was coming her way would not see her, would not care about a pony-statue, would not step on and crush her, would just pass her by.
And then something bumped into her. There was a yelp, and a thud, as the “something” tripped over Twilight's stone-form.
“Uh... girls? I think I found her.”
“What in tarnation? How'd she become a statue?”
“Oh... my...”
“We found you! Tag! Now you're it! Hihihi!”
There was a roar, and the earth shook.
“As much as I hate to interrupt – but I think that dastardly star-bear found us.”
-/-
That last roar was close – far too close.
“Urgh... You could lose some of those stony pounds, sister.”
“Rainbow! You're not gonna make it if you carry her!”
Twilight's heart sunk like a rock.
The mare – Applejack, she remembered now – was right. Assuming a weight equal to that of a rock with a volume similar to that of her own body, the pegasus would have little chance of escape. The only logical course of action would be to leave Twilight behind.
She could only hope the Ursa wouldn't be interested in a pony-statue – that it wouldn't simply smash her out of rage. That it wouldn't smell the trace of pony on her stone-hide. Maybe it would just go past her. Maybe she'd have luck –
“No way, AJ! I'm never leaving a friend behind!”
Twilight boggled.
“What?” was all she could think.
What reason did these five strangers have to help her, on the risk of their own lives?!
“No, Rainbow, Ah meant y'all should let me help ya carry her!”
Despite its scientific impossibility, Twilight felt a sense of warmth flow through her petrified-pony heart.
-/-
One narrow escape from death by giant star-bear, and another encounter with a cockatrice later that ended quite differently than the first, six ponies stumbled out of the woods, battered, bruised, but with a laugh on their lips and a smile on their faces.
“I still can't believe how you just... out-stared a cockatrice, Fluttershy! That was so awesome!” Rainbow Dash gushed.
The shy pegasus blushed, hiding under her mane when everypony turned to look at her. “Oh... I... uhm... oh my...”
“How did...” Twilight shook her leg in an attempt to get rid of the cramps. “How did you even know I'd gone into the forest?”
“Well, darling...” Rarity began, but halted, glancing at something behind Twilight. “I suppose there is someone else who'd be better suited to explain.”
Twilight turned, just in time for Spike to throw himself at her and squeeze the air from her lungs with a fierce hug.
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~~~
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Doctor Hornfield finished his examination, and Celestia tensed.
“Can you help her?”
But she could already see it in the stallion's expression.
“I'm afraid I have nothing to offer, your highness.” He shook his head. “Nothing you haven't provided for her already.”
“This is far beyond anything I've ever seen... Any... normal pony with her symptoms should have been long dead many, many times over.”
Celestia flinched. A stab right in her heart. 'You'd make an extraordinary assassin, doctor,' she thought.
“Your highness, may I... may I inquire who she is...?” The stallion trailed off, noticing the black alicorn's gaze snap firmly to him. Her fangs bared, sending the elderly unicorn taking several steps back.
“Forgotten...” Nightmare Moon breathed. “...How?” She paused, eyes going unfocussed for a second.
Her eyes snapped wide open, locking onto Celestia. “You...!”
“They... forgot...” The alicorn seethed. Shakily, she raised an accusing hoof at the princess.
“You... made...” A heavy series of coughs cut her off. For a moment, Nightmare Moon just breathed heavily, eyes going in and out of focus, struggling to stay conscious. “You... ma... made... for...get... own... sis...ter...”
“BECAUSE THEY ONLY REMEMBERED THE MONSTER!” Celestia roared. “YOU DIDN'T LEAVE ME A CHOICE!”
“THEY TOLD THEIR FOALS STORIES OF THE DARK PRINCESS THAT WOULD EAT THEIR SOULS IF THEY STAYED OUT AT NIGHT!“
“THEY CREATED AN ENTIRE HOLYDAY DEDICATED TO CELEBRATE THE BANISHMENT OF A MONSTER! I SAW THE PUPPETS THEY MADE TO BURN IN THE BON-FIRES! THE PUPPETS WITH YOUR CUTIEMARK!”
“I TRIED, AND TRIED, AND TRIED TO STOP IT, BUT WHENEVER I STOPPED IT IN ONE TOWN, THERE WAS ALWAYS ANOTHER THAT DIDN'T, THEY JUST KEPT INVENTING NEW TRADITIONS AND TOLD NEW AND EVERMORE TWISTED TALES!”
“I HAD TO MAKE THEM FORGET YOU!”
Celestia stood, legs trembling, breathing heavily. Shakily, she wiped a hoof across her eyes to clear her vision.
Only then, she realized the Nightmare had passed out again – and Doctor Hornfield had fled. She would have to do damage control on that, she really didn't want to deal with the royal rumor-mill at the moment.
Celestia slumped on the floor.
“What was I supposed to do?” Celestia whispered quietly. “What was I supposed to do?”
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~~~
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Twilight and the five mares stepped into Celestia's bedchambers. She glanced up one more time at the tiara, the Element of Magic – her Element.
The others looked in awe at Celestia's bedchambers, but Twilight had seen it all before. Instead, her gaze immediately locked onto the nightmare-black alicorn.
The Nightmare had woken, but there would be no chance it could do anything to stop them now. The light of the Elements pulsing around their bodies. Twilight Sparkle felt the energy flowing through them, the warmth of her new-found friendship given form, surging, building up to its release.
The Nightmare spoke, what surely would be its final words.
“No... No... Don't...” Nightmare Moon rasped hoarsely. “No... Not... again... Can't... Not like... this... No...” In an effort to lift herself, her hooves weakly struggled to find purchase on the bedsheets, but failed.
“No... Don't... No... please... no...” Nightmare Moon slumped in her bed.
Twilight Sparkle hesitated.
The magic faded.
And then there was a blur of yellow and pink.
“Fluttershy?!” Rainbow cried out in disbelief. “What are you doing?!”
“Oh, you poor, poor thing...” Fluttershy gently stroked a hoof through the unconscious alicorn's mane.
Fluttershy.
Fluttershy, the meek pegasus who startled at her own shadow.
Fluttershy was petting Nightmare Moon's mane.
Rainbow Dash immediately rushed over to grab her, but Fluttershy seemed more than determined to stay by the Nightmare's side.
“Did you forget the horrible nightmares she sent us?” Rainbow exclaimed, momentarily forgetting the nightmare incarnate was merely dormant. “That dream where you lost all your animals?”
“O-of course I didn't f-forget...” Fluttershy shuddered visibly.
Rainbow Dash flinched, guilt flashing over her face to have done so much as to remind the timid animal-caretaker of the horrors she'd seen that night.
“Of course I didn't forget.” Fluttershy repeated, this time more firmly. “But those were just bad dreams, Rainbow.”
Fluttershy broke eye-contact to monitor the dark alicorn's breathing.
“Nightmare Moon is really, really sick,” Fluttershy spoke quietly. “And that's not a dream.”
There was a quiet groan.
Everypony froze at the sound. The Nightmare had awoken. She was looking at Fluttershy.
“You're not so scary,” Fluttershy shook her head. “You're weak –”
Nightmare Moon's face contorted into a scowl. “More... nightmares... for... you,” she spoke in a growl that sounded threatening, even through her halting speech.
“You're weak, and frightened,” Fluttershy continued, as if nothing had happened at all. “So you lashed out at us...”
“This isn't right...” Twilight paced back and forth nervously. “Princess Celestia told us to use the Elements on Nightmare Moon...”
“Dunno...” Rainbow Dash shrugged. “She seems pretty beat to me.”
“Somethin' ain't right here. Ah think we gotta have a talk with th' princess.”
Twilight turned to leave, when suddenly –
“Hey, Queen Moony.” A subdued Pinkie Pie had joined Fluttershy at the Nightmare's bedside. “Why did you want to make the night go on forever?”
Twilight opened her mouth to explain the legend – but something about seeing the otherwise chipper and bouncy pony so quiet and reserved made her pause.
“H... hate...”
Twilight's ears folded back. But Pinkie Pie merely tilted her head inquisitively.
“They... hated...” Nightmare Moon spoke in a sickly, scratchy voice. “...Me.”
Pinkie's ears wilted. “I don't hate you.”
If the room had already been quiet before, now it was dead-silent. Everypony was staring at Pinkie Pie – including Nightmare Moon.
Then the silence was broken by a sound. It was a strange, almost in-equine garbled noise that sounded too low-pitched, sounded wrong. Nightmare Moon shook in her bed. All the while, Pinkie kept standing in place, a small smile on her face.
It took Twilight a few seconds to realize Nightmare Moon was laughing.
Twilight shared a glance with her friends.
“We definitely need to talk with Princess Celestia.”
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~~~
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Time passed. Arguments were made.
Tempers flared. Two big sisters butted heads over their younger siblings.
A conclusion was reached.
And so, Twilight and her friends found themselves in the Nightmare's presence once more.
Getting the Elements to activate was easier this time.
-/-
“Rainbow Dash, who didn't abandon a friend, even at risk to her own life, represents the spirit of... Loyalty!”
“Pinkie Pie, who overcame her nightmare and showed all of us there was nothing to be afraid of – in more ways than one – represents the spirit of... Laughter!”
“Rarity, who gave herself up to the Royal Guards to buy us time, and who sacrificed her chance with the Canterlot Elite represents the spirit of... Generosity!”
“Fluttershy, who showed compassion, even after what Nightmare Moon did to her, represents the spirit of... Kindness!”
“Applejack, who stood up to Princess Celestia and told her the truth, represents the spirit of... Honesty!”
“The spark ignited inside me when I realized that you all are my... friends.” Twilight exchanged warm glances with the five mares she could not believe she had only met a few days ago. “...But we do not seek to destroy the Nightmare. We want to give her a chance, both her and Luna, to seek out friendship.”
Twilight spoke the words. Then there was a rainbow.
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~~~
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“Why?” Luna-Moon asked, their voice weak, though not for reasons that had anything to do with their newly regained physical strength.
Celestia's hug only tightened. At first, Luna-Moon went stiff in Celestia's embrace, caught off guard and completely at a loss how to react, their face fraught with conflicting emotions.
But eventually, cautiously, they accepted the hug.
“Because everypony deserves a chance,” Celestia whispered, her own voice heavy with emotion. “I... I just needed somepony to remind me of that.”
Luna smiled. And, for the first time in a long time, Nightmare Moon smiled alongside her.
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Author's Note
Go check out Sandstorm94's officially endorsed "unofficial sequel", Redemption of a Nightmare! 
This story was originally a writing prompt I posted myself, which inspired Eruantalon's story “The Nightmare Crumples”, which in turn motivated me to take on my own prompt. 
This is sort-of an experiment. I want to see how people will receive this – I'm not 100% happy with this story myself. 
I know there are pieces missing – believe me, I tried to fill them in; I tried for 2,5+ years – and I am still left with the sense there is so much wasted potential here, especially in examining the character-dynamic between Celestia and a sickly Nightmare Moon. 
I guess sometimes the muse just goes on strike. 
I suppose if anypony else wants to take up the slack, be my guest. This was originally a writing prompt, after all. 
PS: Thanks to FanOfMostEverything for coming up with the punny chapter title "Over the Moon, Under the Weather" while brainstorming a story-title. 
PPS: With all said above, if you want to see more „cute“ from me, but... well, written better than the above story, I can recommend taking a peek at „Pinkieviduality“, starring a happy-go-lucky Pinkie-clone at a traveling circus.
