Luna drifted through the air, her wings gracefully lifting her above the clouds. The harvest moon shone brightly, with its children sparkling right beside it. The princess closed her eyes. This, now, this was the best part of the night. Her evening flight, away from the castle, away from other ponies. Luna took one last breath of fresh night air and slowly descended. Her hooves gently touched the ground, and she sighed in contentment.
Of course, she then remembered a dream she had a few nights ago. It wasn't much, it was just a dream, but it troubled her so. Luna hadn't been able to stop it, which she could with other dreams. And she did want to stop it.
Luna had dreamt she was always angry, angry at Celestia, for many nights. Then she had burst out at her sister, and turned into... Well, she didn't exactly know who or what it was, but it scared her. After a fierce battle Celestia had sent Luna to the moon.
She wouldn't do that in real life, would she? Luna's brow furrowed. Her sister would never banish her. Especially not to the moon.
Luna snapped out of her daydream (well, it wasn't really day though) and realized it was time to lower the moon, and wake Celestia so she could raise the sun.
But then she woke up.
Dust. Dust and rubble... That was all she could make out of her blurred vision. It was dark... And cold... Luna shivered. Where was her sister's bright, welcoming sun? Luna coughed, but no noise came out of her mouth.
"Hello?" Luna tried to say as loud as she could. She felt her lips form the words, but no sound escaped. She saw clearly that she was on a dull gray, rocky terrain. Where was the soft grass? Where were the bright flowers?
Where was the sun?
Luna's eyes darted around the sky, searching for the sun. Her gaze then laid upon the green-blue planet. Earth. There it was, right in front of her. But if Luna was not on Earth, where was she...?
Oh no. No, no, no...
The Moon. She was on the Moon, of all places... Why? Why would she be at such a cold, desolate place? Luna took a deep breath (despite her cracked ribs) and tried to rise to her feet. Her mouth opened as if to cry out in pain, but no sound. Of course, She thought as she lowered herself to the ground. No sound in space... Luna's horn lit up, and now she could hear. But what was there to hear, other than her own voice? What was she expecting, birdsong?
Luna looked down at her hooves. They were chipped, cracked, and covered with the gray dust of the moon. Her right leg... Slightly twisted, not to mention bleeding. She wiped blood off her lip with her left hoof. Luna turned her sore neck to check the condition of her wings. They didn't hurt too bad, but she couldn't fly with them either.
In the distance, she saw something shine.
Luna limped over to it, but when she lifted it with her magic to see it, she immediately threw it down again. It was ~~her~~ Nightmare Moon's helm.
Celestia... Sent Luna to the Moon. Celestia sent her there. Celestia...
Why did her sister do this? Celestia should've saved Luna, not banished her. Celestia had the Elements! She should've saved Luna from the Nightmare, then all would be well. But even if Celestia absolutely had to banish Luna, why to the Moon? It was so far away... Did Celestia want to be as far as possible from her? Was her sister too... Busy to even care? Like, 'Oh Luna, what's gotten into you? I don't have time for this, goodbye.' Luna imagined Celestia saying.
The realization of what her sister had done to her suddenly made itself clear. Celestia didn't love Luna! She knew that now. Her hatred boiled inside of her. Celestia... Always putting herself before others... Always the center of attention...
Celestia... Always treated Luna like she was dirt...
What had Luna done wrong? Nothing. It was Celestia's fault.
Luna rose to her feet. Hot pain shot all along her body, but she welcomed the pain."It's not my fault...It's not my fault... It's your fault, all your fault... Not mine. Oh, it isn't my FAULT!" Luna screamed, tears streaming down her bruised face. "IT'S NOT MY FAULT!!!" Her throat was on fire, but she did not care.
Luna's eyes blazed with fury, and her horn glowed brightly. "Why?!? Why would you do this to me?!?! I KNOW YOU HEAR ME, CELESTIA!" Her tears washed the dust off her face. "ANSWER ME!!!"
Silence.
"Of course. Just as I thought... You don't CARE." Luna blasted the sky with her horn. "YOU NEVER DID CARE!" She choked on her sobs as she gazed into the cold, unforgiving sky. "I HATE YOU!!!" She screamed with all her might, as loud as she could. "I HATE YOU!" Luna screamed and screamed, until her shouts faded to whispers, and she quieted. The strength in her voice was gone.
The Sun started to peek from behind the Earth, but the exiled princess felt no joy from its light.
The days turned to months, months to years, years to decades. But to an immortal, the time would seem shorter, wouldn't it? At least that's what Luna asked herself every single day. The time seemed to pass agonizingly slow.
Wait--- Luna didn't even know if Celestia would ever let her return home.
Luna's brow furrowed. She hadn't thought of that. It was just an automatic assumption that Celestia would let Luna return soon enough. After all, Celestia was a kind pony. Luna knew Celestia loved her dearly... But the nagging at the back of her head said otherwise.
The nagging was always there. In fact, it had turned her into Nightmare Moon. It had told her Celestia was cruel and selfish.
And Luna had believed that.
Why? She obviously knew otherwise... Or did she... Her memory of Celestia was blurred. How long had she been exiled?
How could she have been so stupid? Why did she let the Nightmare turn her into a monster? Why did she rebel against her sister, when clearly she knew better? It was, in fact, Luna's fault after all. This troubled Luna greatly. She could never forgive herself... Her horn glowed brightly. A small ball of shadow appeared.
"You will make sure I never forgive, and most of all, forget, Tantabus." Luna whispered to the shadow. Surely this would make sure she wouldn't turn into Nightmare Moon again.
Surely this would stop her so-called friend, the Nightmare, from grasping Luna's thoughts.
Luna smiled at that thought. "You will make sure I am sorry for my past deeds!" Her expression was fierce. "PUNISH ME!" She commanded the Tantabus.
Surely the pain would forbid any forgiveness.
Stars. They gather. They dance around the moon. They are ready. Ready to free their mistress.
It is time.
"Why are you here?" The exiled princess asked the stars.
The four stars' voices resonated across the moon's surface. "We were summoned. We serve you, princess."
"I did not summon thee." She gritted her teeth. Luna did not deserve to leave.
"But you did, highness. We heard a call across the galaxies."
"I DID NOT SUMMON THEE." The moon princess sneered.
"Then, if I may, mistress... Who did?" The youngest star ventured.
You must leave this wretched place. You must have revenge, Luna, don't you understand? This is beyond your control.
"I..." Luna could not think of anything to say in reply.
"Mistress?" The young star said rather sheepishly.
The Moon Princess sighed and turned to the four stars. "I am ready."
"For what, princess?"
"I am ready for thee to take us home. After all, I am dying to see my dear sister." Luna smiled, revealing sharp, pointed teeth, and her pupils turned to slits.
And with that, the princess left her prison to seek revenge.
Author's Note
Of course, the rest of the story would be the pilot of the show 
Sorry this took me so long. I had severe writer's block...
