"Your Highness, we have a criminal."
Queen Nightmare Moon looked at the bat pony mare who had just entered the room. "Midnight Blossom," she answered. "What crime has the offender committed?"
"She has a cutie mark of a heart surrounded by rays of sunlight, Your Highness, and she refused to have it removed. We would have had her executed in the square, but she pleaded to speak to you. If you are available, she is currently in the dungeons."
"Bring her here, Midnight. If she wishes to speak to me, then I will make myself available."
"Yes, my queen," Midnight said. She left the throne room and the doors clicked shut.
Five minutes later, the double doors were thrown open. Midnight Blossom and a bat pony stallion dragged a mare behind them. Nightmare could not see her, but could tell by her voice.
"Let go of me!" She shouted at her captors. "I wish to speak to the Queen without your hooves on me. It's not like I'll do anything like run away or attack her. If I move, I'll be killed!"
"Let go of her," Nightmare Moon told the guards. They obeyed immediately and stepped back a few paces.
This allowed Nightmare to look at the prisoner properly for the first time. She was a unicorn, about fourteen years old, with light blue eyes and a short mane with pink, green, blue and purple stripes. The mare stood tall and proud despite the circumstances. She looked away: she would not look directly at somepony who looked so much like her.
"What is your name?" Nightmare asked.
"Aurora Sky, your majesty," she replied.
"For how long have you had that cutie mark?"
"A couple of months. In the village where I live, there are few guards. I used saddlebags to disguise it. Your guards raided it yesterday and found out about my mark. I was offered a chance to give it up but refused. When they said that they would execute me, I told them that I wanted you to be the one to do the deed."
Nightmare was taken aback by this mare's bravery. "Why do you want me to do it?"
"The guards don't deserve such a horrible job. They are not the monsters everypony thinks they are. They don't hate the ponies whom they punish. You, on the other hoof, are a monster devoid of emotion. Surely you can do such a simple task, hmm?"
There was no questioning that Nightmare Moon could. "Fine." She prepared to cast a spell, but was interrupted when Aurora snapped, "Look me in the eye!" She did, and observed those eyes as blue as the old sky, the sky in which Celestia's sun shone so bright. She observed that wavy mane, shorter than Celestia's but the same colours. She realised that she couldn't kill this mare.
"Hmm, it seems that you can't," Aurora mused. "I am at your mercy. You are merciless. Except that is not true. You couldn't get rid of your sister completely, and you can't finish off her lookalike, either. We are taught in school that she is a monster, but that's a lie too. How many lies have you shrouded yourself in, to make you who you are now? How much of the old Princess of the Night remains? Do you miss your sister at all?"
Nightmare Moon could barely speak. "You - you - you dare speak to me like that?!"
"I know there is more to the story than you wish to tell. The meaning of my cutie mark is that I spread light and truth. I can..." She searched for the right words. "I see things. When I look at you, I see the old you, the real you. The blue alicorn with the short light blue mane. Scared and furious at yourself for what you have done. I can also see you and your sister, before you banished her."
Those words made Nightmare Moon remember.
Nightmare Moon towered over her defeated sister Celestia. An anti-magic collar hung around her neck and her back hooves were chained to the wall.
Nightmare laughed, "Look at you, Celestia. You are at my mercy, and I am merciless. Prepare for your demise."
"Don't do it, Lulu," Celestia whispered.
The evil sister's blue-black horn glowed, and she stared into her sister's purple eyes. Neither sister turned away. She saw sadness, fear, disappointment, in her older sister's eyes. She saw all of those times that they were together. Her confidence drained.
Celestia sighed. "I knew that you would come round. You will likely banish me to the moon or somewhere like that, but you won't kill me because you still love me. Send me if you so wish. When I return, I shall love you still despite your mistakes and hope that your love hasn't gone completely by then."
Nightmare Moon cast a spell, and Celestia disappeared. She held the chains and tears spilled down her cheeks. "I love you, Tia," she said softly. "But you are as much of a monster as I am."
Nightmare looked at Aurora again. "You are an interesting mare, Aurora. You are correct. I miss my sister, and much of what I have done is out of fury at myself. I am not strong enough to reverse the spell that sent her to the moon, and unable to reverse the mistakes I have made over the last century. You seem as good a mare as any to help me. Would you please?"
Aurora casted a spell. She grew taller; her mane and tail became longer and flowed in an invisible breeze; huge wings appeared by her sides; her cutie mark switched to an actual image of the sun; her horn grew much longer; and her eyes became purple. Midnight Blossom and the male bat pony backed away from her.
"I am here, sister," Celestia spoke, her voice calm and regal. "I am so sorry that I could not prevent this, and that I did not look after you when you needed me. I am here to right those wrongs. You and all of your guards have amnesty for what you did during my absence, if you can stand by my side again, Luna."
"I am a monster, sister, I am scum," Nightmare Moon said. "How can you trust me again, even after all that's happened? I betrayed you twice."
"I can trust you because I know that you want to make the right decisions. The Elements of Harmony have returned with me, and await further instruction. We can make this world a better place, Luna."
Nightmare Moon strode over to a window. She slowly changed back into her old self, Princess Luna. Her mane and tail became such darker and flowed like Celestia's; she shrank slightly; her coat became lighter, no longer blue-black but midnight blue; her pupils dilated until they were normal size and not slitted; her wing feathers split into smaller feathers; and her armour fell away.
Once Luna's transformation was completed, Celestia joined her by the window. Luna lowered the moon and Celestia raised the sun for the first time in over a century. They watched the eastern sky fill with pink streaks and the orange orb that now hung in the sky brought a new era of peace and happiness to the land. There was much to be done to heal the wounds she had inflicted upon the land, but for now Luna just watched the sunrise with her sister by her side.
Author's Note
Just a random one-shot I came up with. The story sort of built itself as I wrote. I don't intend to write a sequel, but if you all really want one, I will come up with something.