Description
Princess Celestia and Luna weren’t the only princesses. There once was 3. There once was even a princess of friendship, but its been a long, long time since then. Her name was Dusk, Princess Dusk. She was loved dearly by her older sisters, and the whole of Equestria. Being the youngest of the 3, she was very sheltered as a child, almost never leaving the castle. Most of her time she spent in the library, reading books about ponies going on wild adventures, making all sorts of friends. She wanted that.
One day, she snuck outside of the castle walls, and into the town. There she meta group of ponies who she fell in love with. They were everything she ever wanted, true real friends. Ever since that day she began sneaking out of the castle to go visit them. They were her everything, when a powerful foe came to Equestria, Dusk and her friends managed to save the young kingdom, with the power of friendship. When the war was over, she was dubbed the princess of friendship.
Now being able to freely spend time with her friends, she spent most of er days with them, they were everything to her. Celestia was fearful of her getting so attached, knowing that one day her friends would pass, and she would continue to live, for a very long time after them. But Luna assured her that it would be ok. She had never seen her baby sister so happy before, and she wanted that joy to last forever.
For a while, things were good, more than good. But life went on, Dusk's friends began to age, and Dusk didn't. Dusk yearned to live a normal life with her friends, to grow and age. She couldn't imagine living a life without them. So began to do research, she knew her friends wouldn't want their lives extended, so she had to find a way to become a normal unicorn.
One day, she found an old, weathered spell-book that contained the spell she so desperately wanted. With no hesitation, she performed the spell, turning herself into a regular unicorn. When Celestia discovered what she had done, she was furious, her baby sister had permanently changed her life, for forever. Celestia kicked her out of the castle, forbidding her from ever returning. Luna was devastated, knowing that she would have to live one day without her baby sister. She begged Celesita to let Dusk return, but she refused. The walls she had built up around herself to prevent her from hurting when her subjects would pass were coming crumbling down around herself, now being forced to reconcile with the fact that one of the ponies she cared most about would pass, and she would have to continue to live.
After that, life went on, Dusk was cherished by her friends, as if nothing had changed. Dusk was still Dusk, Alicorn or not. Luna would visit Dusk, as much as she could, not wanting to miss a day of what precious time they had left. Celesita refused to visit her, the pain of losing her would be too great, and she felt that of she distanced herself from Dusk, it would hurt less, feel more survivable.
Life went on, Dusk aged, and Luna and Celestia didn't. When the time came, Luna sat at her bedside, she had begged Clestia, just to come this once, the last time she ever could, but she refused. Dusk never regretted her decision, even now. She gave Luna a letter, made for her and Celestia. She had lived a good life.
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Inside the letter, Dusk told them of something they didn't know about the spell. In order for her to become a unicorn, her power would have to be transferd to another. One day, she would be reincarnated, as a new unicorn, but it would be a very long time until then. Since then, Luna and Celestia kept an eye out on all of the unicorns of the land, hoping to find something that would indicate that it was their baby sister.
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When little Twilight Sparkle came into her academy, Celesita knew. She looked almost just like her baby sister, right down to the cutie mark. In that moment, she made a promise to herself, that she would make her an Alicorn again, some way, some how, she would make sure she never had to live through her baby sisters death again.