Don't own MLP, etc.
It was a conspiracy. It had to be. Sure the pressure had always been there for her to abandon her books, to shirk her responsibility to knowledge for some petty friends. The very moment, the very SECOND that she had discovered the evil that Celestia had given birth to, Twilight had been whisked away, given the so called 'duties' of overseeing a celebration that was completely and totally under control.
The books told the story. Celestia tried her best to make sure everyone though it was a myth, a legend to scare ponies at night. But she knew the truth. Celestia had trapped her sister in the moon. No longer content to be the power of the day, Celestia turned her eyes to the dominion of her younger and more naive sister. For one thousand years, the lies spread by the Princess had gone unquestioned, no longer.
It was difficult. Ponyville was entirely made up of co-conspirators. Everyone tried to drag her away from her books, from the knowledge she needed to end the tyranny wrought upon them by a mare discontent with her power. "The victor writes the history books." This was something she knew, but other ponies had forgotten along the way. She could no longer remember, but she knew Spike wasn't her true brother. How stupid could the Princess think she was, to tell her an entirely different species was her own kin?
But there was a chance. Celestia had grown in power, considerably grown, but the trap she had placed on her sister only lasted one thousand years. It could be renewed permanently, but for one single night, the dictator who had lied to every pony in Equestria for one thousand years would be weakened. For one single night, she could rewrite the history books, prove to the world that the so called myths were in fact partially real, though distorted by the demented Celestia.
Magic always had its price, but one thing about magic was that most spells could easily be made with the ingredients from a single animal, a dragon. And so it was, while the conspirators of the Princess partied on below her, she dragged her 'brother' upstairs, slit his throat, and let the blood pour down into a golden chalice.
Audite me, o deorum. Quaero vindictam. Pondera in statera wyrd regina. Dimitte soror oblivio. Insidias perdere coniuratos vile est princeps. Et historia est tale ostendunt!
She poured the blood of her 'brother' onto the runes already carved on the floor. Gathering in a perfect circle in the middle, life's elixir wavered, then sunk in, revealing a rough and milky white surface. A short distance away, chained between two great pillars, languished Luna.
"How did you come here young pony?" she wheezed.
"I know the true story. If I release you, can you stop your sister?"
A tired smile spread across the great spirit's face. "I am still the governor of the night, even if my role has been filled by a pretender."
With careful hooves and a delicate touch of magic, she released Luna from her bonds and brought her back into the world. Spike's cold corpse had already begun to decompose, Dragons did not last long on the mortal plane after death. She hoped that hell would exact a greater punishment than her simple spell ever could.
Yes, no longer would the light of deceit blind the eyes of the common pony. It was time for the cold hard night to show the shadows for what they really were.