Celestia watched the shambles of the world she once called her own, destroyed by the one who she once called her own, taken by the one she called her enemy. Her sister, Luna, lay in pain, mentally and physically destroyed by the one she felt truly understood what she wished to protect, yet could only watch as she made the mistakes she once made. Both lay pained, unable to move, fight, and even shine a light on the darkness in their castle. The guards, once sworn to protect, abandoned, manipulated to their new enemies side. What had come of the land they had called home? All that lit up the bedroom in which Celestia once slept was the blazing fires outside, the cries of help from the many ponies of Cantalot. Their moon and sun switched hour on hour, leaving the ponies restless where they lay. Their magic was drained, their bodies weak and bruised. They could only hope the rest of the elements of harmony could somehow work together to rid the world of this curse.
Luna lay in the far corner, cuts and bruises across her body where she fought many creatures of the night which turned against her, from timber wolves to bats. Her magic was drained from her battling the guards who turned against her. She watched Celestia, and almost cried out seeing her struggle. Whereas Lunas magic had only been drained, Celestias horn had been smashed, blood pouring through it, down across her face. Celestia gave a strong face, yet her will to cry almost made her give in, to curl in in tears, wishing for comfort like a child. Luna has far gone past this stage, watching the struggle of those around her the ones she watched over, turn against her in an instant, and it broke her heart. How her sister watched her do this was more heart breaking than Luna could hope to imagine, to see it happen again must be hurting Celestia more than ever. She had already gone through the agony of it before seeing sunset shimmer leave her, turning her back on her and leaving their universe all together for her pursuit of power.
They looked at each other, both secretly wishing to curl up in each other's hooves, to feel love again. They simply looked into each other's eyes, Celestia seeing the confusion in Luna's, Luna seeing the pure pain in Celestia's. They heard bangs outside of their room. Their two remaining guards which never left the princesses side began calling out. They were not afraid to put their lives on the line for the two princesses.
"Stay back! Do not come any further!" One of the guards called out. Luna felt the fear in his voice. It pained her, but she knew the inevitable would become of them. When she heard their calling out in pain, Celestia put out her hoof to stop her running to help them, to protect them, the last two ponies in equestrian who remained at their sides to their end. She heard them fall, the thump of their bodies, the unsteadiness of their hooves, as they rose back up to her side, the last members of equestrian to fall to her.
Before they could stop to think, a light shone into the room. They glimpsed up, putting the last of their strength into it in fear of blacking out.
Twilight Sparkle stood at the doorway in the dress she wore the day she earned her princess title, her crown firmly on her head, now decorated with a dark and black element of magic. Once the sight of her brought hope, now it brought fear. Discord stood in the shadows behind her, proud of his "convincing" skills to let Twilight let out her full abilities.
He looked back on the events that had unfolded, placing his magic on the young princess, as she believed she was simply getting tested. The fall of the rest of the element's, who stayed to her side as the elements reacted to the new dark magic. Each element became discorded in turn to Twilight's, each pony begun their reign of havoc. Rainbow dash used her flying abilities to attack Cloudsdale. He had the joy of seeing Fluttershy turn back to her discorded self, making the animals turn to her side for discord to turn them into beasts. Rarity became selfish, taking on Canterlot and mercilessly attacking them, whilst taking the gems all to herself and making them treat her as "the leader everypony should know". Applejack became dishonest, lying to her family and leaving them to use her element against Appleloosa, lying to them and making them work for her. Pinkie Pie became hateful, taking on Ponyville and bringing hatred and cruelty to the ponies. Twilight, in turn, used dark magic, against all those who followed. She left her friends, and decided to take on the princesses single handily.
Suddenly, bright sparks powered into her horn, her eyes red ablaze, her coat taken to the new dark purple the power of disharmony has done to her. Her eyes closed as she focused, Discord behind her stopped her anxiety giving her second thoughts on her actions.
"There can only be one princess in Equestria…." Twilight said confidently, a look of determination on her face. Her horn powered magic of black and purple. The sister's eyes widened in memory of the day Luna fell to darkness, repeating these same lines.
"…And that princess…" Celestia's thoughts turned to the ponies she promised to protect. Shining Armour and Mi Amore Cadenza's home in the Crystal Empire had been ridden of its hope, Ponyville was left in darkness, and the animals of the Everfree forest had sunken into the shadows, before being taken by it. She left herself with a thought". "Those who do not learn from History…"
"…WILL BE…" Celestia closed her eyes in sadness, seeing twilight meet her dead in the eyes with pure anger, her faithful student's mind destroyed by the one they called their ally.
"ME!" The room lit in light, and discords smile grew, as he watched the two princesses flinch away from Twilight's magic.
"…Will be doomed to repeat it" muttered Discord.