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// Celestia Overwhelmed 
// Story: Sun and Moon: Daybreaker and Nightmare Moon 
// by RainbowSparkle3 
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Searing pillars of flame gushed out from the castle floors as Daybreaker laughed maniacally, the geysers of fire perfectly matching the color of her swirling, blazing mane. She walked towards the stock-still Nightmare Moon; the strong, proud, and above all, feared princess now reduced to a play thing for the terrifying Daybreaker.
Luna and Celestia finished their conversation, and the Sun Princess was ready to defeat the Evil Royal Sisters. Daybreaker smiled as she charged up a magical beam to vanquish Nightmare Moon once and for all, and Nightmare gathered up the last of her strength to defend herself. 
Just as the two fired their respective beams of red and blue, Celestia teleported between them, intercepting their clash. "You can't destroy me, I'm everything you want to be!" Daybreaker said, continuing to blast at Celestia's right wing, with Nightmare shooting at her left.
"No, you're not! You are not real, and you will never exist again!" Celestia declared, waving her huge wings up, deflecting their beams. Right before Celestia had finished her sentence, Daybreaker felt a chill running down her back, warning her of something bad to happen. Nightmare must have felt it too, for simultaneously, they used teleportation just as Celestia deflected the attacks. 
They both popped up to opposite sides of Celestia, to her great surprise, and in unison, Daybreaker and Nightmare Moon quickly shot a beam at her, zapping her and rendering her unconscious almost instantly, but not before she could utter three words. "Sister...Starlight...ruuun." On that last slurred word, Celestia's eyes shut and she collapsed onto the red carpet of the hard, flaming floor. Starlight and Luna, who were anxiously watching in the background, both gasped as the glorious princess of the sun fell. Contrary to her last instructions, Luna quickly flew to Celestia's side, shaking her and calling her sister's name repeatedly. Starlight, fortunately, couldn't put herself in Daybreaker and Nightmare's path, as she was trapped in an immobile bubble. Instead, she watched from the sidelines with worry.
Both of the Evil Sisters laughed at Luna's futile attempts to wake Celestia. Then, not paying anymore attention to her, they turned to face each other to continue their duel. "Now that my meddling counterpart won't get in our way, I can tear you apart without any worry of being disrupted!" Daybreaker shouted, quickly flying at Nightmare, who was gathering magic in her horn. Daybreaker lowered her head, and fire engulfed her upper body completely. Nightmare braced herself for the attack, but Daybreaker flew around her, taking her by surprise. She headbutted Nightmare in the chest as she spun around, sending her crashing into the throne in the back of the room.
Nightmare groaned, and slowly rose from the rubble of the seat she had flown into. However, Daybreaker was quicker, and used her magic to direct all the burning pillars at Nightmare. The night princess yelled in pain as the incredibly hot flames blasted and engulfed her in a sea of fire. Starlight was watching this battle with horror, and she was yelling at Princess Luna to look.
Startled out of her attempt to wake up Celestia by Starlight's urgent command, Luna swung her head around, and the sight she saw terrified and angered her at the same time. Though she knew she didn't have her dream powers at the moment, she had to try to stop Daybreaker, no matter how bad Nightmare was. After all, this was still Starlight's nightmare, and as she had stated previously, such a sight could have a grave consequence on Starlight's psyche.
Luna roared and charged Daybreaker, who was cackling at Nightmare's suffering. She spun around, and easily blocked Luna. Nightmare, though, while Daybreaker wasn't looking, had managed to drag herself out of the inferno, though heavily wounded with burn marks all over her dark body, which was even more black than before. While Daybreaker lazily blocked Luna's attack, her eyes showing boredom, Nightmare narrowed her eyes in fury at the back of Daybreaker, and she powered up an attack so fierce, Daybreaker could feel the raw amount of energy radiating from Nightmare's horn, which was also distorting the air around it.
In an ironic twist, now it was Nightmare who attacked when Daybreaker spun around. This was her strongest technique, Nightmare Fury.
Nightmare Moon's horn shone brightly with blue for a single moment, then she fired her spell at Daybreaker, turning the whole world black. The only pony who could see was Nightmare. Even if Discord were here, his awesome powers wouldn't have been able to break this spell. Along with sight, Nightmare's technique made it impossible for her to be heard, smelled, or touched. However, Nightmare could touch Daybreaker, which she did.
Daybreaker tried to see any glimpse of light, but to no avail. She then tried something else, she lit up her horn with a bright fire, but it didn't illuminate the darkness. Neither did her blazing mane. So, out of ideas, she simply waited in the dark, bracing herself for any incoming attacks. But, it seemed this was Nightmare's most powerful spell for a reason. This black world amplified her power more than 10x, and it cut the strength of everypony else by half, which would make somepony she was 20x weaker than on equal standing with her. Of course, Nightmare also had the advantage of the senses, so she was almost unstoppable in this shadow realm.
Nightmare Moon begun her assault. She focused her magic, and engulfed her sister in an ocean of extremely dark power, in payback for the blaze she had been trapped in. Of course, this was an ocean rather than a sea for a reason. It was much bigger than Daybreaker's little pool of fire, so she couldn't get out of it, unless she trudged out for thousands of miles, blind and disoriented, with no way of knowing if she was going to the center or heading out.
Daybreaker shrieked and Nightmare laughed, using her magic to allow it to be heard. Daybreaker shut one of her eyes from the pain and clenched her teeth. She then thought of something else, she could just fly out. So, she opened up her wings, and flapped frantically to get out of this nightmare of pain. Sadly for her (and good for Nightmare Moon), no matter how high she soared, she couldn't get out of this black magic. This was because it stretched above for over 1000 miles, making it similar to it's horizontal size. To even Nightmare's shock, tears started to form at the edge of the proud, malicious princess' eyes, and she started to speak in between sobs. "I'm sorry, sister! I promise I won't fight you anymore, or hurt you! Just please, let me out!" She started to convulse in full on crying, beginning to grab the gleeful night princess' attention. 
Nightmare thought silently, the smile on her lips slowly slipping away. Even though she didn't have the power to continue this much longer, she decided, with reluctance, to end the spell.
With the constant, burning pain finally gone, Daybreaker's blubbering gradually faded away, and she smiled genuinely at her sister. "Th-thank you," she uttered weakly. Then, she went to hug Nightmare. Luna watched this scene play out in shock, then she too, smiled at this.
However, it turned out all was not as it seemed to be. Just before Daybreaker wrapped her arms around Nightmare, her smile stretched wide with menace, and she punched Nightmare in the face, greatly startling her, and rocketing her at one of the walls, and out of the castle. Daybreaker cackled evilly, then shouted loud enough for Nightmare to hear. "You fool! Sentimentality like that is what makes me a much more powerful fighter than you'll ever be! No mercy to anyone, not even family, is the number one rule to being a tyrant! If you had been like me, you could've ended this fight with that last attack! HA, HA, HA!!!" Nightmare halted her drop from the castle, and sighed with disappointment in herself and her sister.
"Of course," she muttered to no one in particular. "I should have just destroyed her, like she said herself. I won't make the same mistake again!" With that, she charged, but completely out of power, even the greatly weakened and wounded Daybreaker pounded her into the ground. Nightmare was demolished. Crushed. Humiliated. Beaten. Any of these words and more would've been a good example of what happened. Tired of this beat down, Nightmare got an idea.
Right before Daybreaker was about to strike again, she disappeared in a flash of light blue. Then, she reappeared next to Luna, to her surprise, and Nightmare's horn glowed. Luna was confused, until she felt her magic being drained, then she figured it out. "N-no. Noooo..." Luna whispered. Then, like her sister, fell unconscious. Starlight cursed at this, then grit her teeth in anticipation of what would happen next.
Daybreaker looked slightly worried now, and she closed her eyes to think. After a few seconds, her eyes flew wide open, and she grinned. Then, her horn glowed in a similar fashion to when Nightmare had sucked Luna's power, and Celestia's body emanated with a faint, yellow light. This magic was being absorbed by Daybreaker, and when she was done, her power was almost exactly the same as Nightmare's, if not exactly equal. 
Now that both princesses were equal in terms of strength, they walked up to one another, glaring. The sisters were ready to start the battle for real.