Luna scowled as she lowered the moon and the sun abruptly rose in its place. Ponies were up now, enjoying the day and rejoicing that the night was over.
See, Luna? They don't care. But maybe, just maybe, if you got rid of Celestia, then perhaps... They would appreciate you more. Nyx purred in Luna's mind. Nyx had this... Plan, but Luna wasn't sure if she wanted to follow through with it. But Nyx insisted that it would work.
~oOo~
Celestia sighed and walked into the throne room, awaiting a pile of scrolls for her to read.
"Not another step!" Luna called, stepping out from behind her throne. To be honest, she didn't really have time to think, she was just doing as Nyx said.
"Luna...? Why-"
"Did you really think I would just stand there when they all... Basked in your precious light?" Luna said 'precious' as if she were saying something repulsive.
"Luna-" Celestia was filled with confusion, and she was quite overwhelmed. "Luna, what's going on?" She started to really worry...
Oh, looks like Nyx already worked her magic. Ooh, such fun! Wait till you see what your own sister does! The voice in Celestia's head mocked.
Celestia's eyebrows furrowed in anger. Shut up. Just leave my sister alone!
"Equestria only has room for one princess... And that princess will be ME!!!" Luna's eyes flashed a blinding white and she stomped her hooves on the ground. For a second Nyx almost made Luna stomp so hard it would make the whole castle fall on Celestia, but Luna held back.
Luna rose up, rising the moon which covered the sun. A sinister amber light surrounded her, encasing her in a ball of darkness. Nyx? NYX? What's going- The amber light turned as misty as the night sky.
Poor oblivious Luna. You didn't see that coming, did you? You were so easy to manipulate. Ha! Perhaps your sister won't be any better. Nyx laughed, her cackling ringing out through the throne room, but that laughter came out of Luna's mouth. Her coat darkened to an inky black. Her delicate crown and accessories turned into armor. Luna's mane grew wild and as mysterious as the night sky itself. Just as her reflection had had that fateful night, she too had fangs for teeth.
"Luna! Lower the moon! It is your duty!" Celestia shouted as she tried not to cry.
Fight her, Celestia! You know you will win! Who cares if it's your sister.
Celestia wished she could punch that voice.
"Hmm? Oh, I am not Luna. Not anymore." It was Nyx talking now, Luna had no control over her new body. "I am... NIGHTMARE MOON!!!"
Celestia barely had time to jump out of the way when Nightmare Moon fired a blast of magic at her. Instead of hitting the white mare, it hit the ceiling. Huge chunks were falling. Celestia swiflty flew out the castle, not wanting to fight her sister.
Luna tried to reign in Nyx, holster what she had become, and tried to speak her own words. "Celestia! We... We were supposed to rule as equals, sister, We just wanted... We just... We just wanted to be loved! Like you were. We... we didn't want it to be like this, sister. Please. Forgive us." Luna said in a strained voice as tears poured down her face.
Nyx got control over Nightmare again. "And where do you think you're going?" Nightmare Moon smiled. She flew after Celestia into the moonlit sky.
And with a mighty blast, Celestia screamed as she fell to the ground. She had been hit squarely in the chest.
Nightmare Moon laughed gleefully.
~oOo~
Celestia slowly got up to her hooves. The Elements... They... Will save Luna...
Pffft. You can't wield them alone. It won't ever work.
Celestia used her magic to bring up a stone pedestal and brought out the Elements of Harmony. She rose up to face Nightmare Moon, face her own sister.
"Oh, back already?" Nightmare Moon scoffed.
"Luna... I'm so sorry..." Celestia whispered. Rainbow light came towards Nightmare, then she disappeared. Her silhouette appeared on the moon, with a faint shout of fury from Nightmare Moon.
"I couldn't save you... I am too weak..."
And then Celestia heard the laughter of that evil voice in her head. And she would never forget it.
"I will see you again, my sister."