Dear Princess Luna,
While I am sorry that I haven't been keeping in touch as much as I should be I have been busy searching for the Shadow of Sweetie Belle. It isn't easy searching through the dreams of thousands of ponies to find a mention of such a Shadow, but despite our failures my sister continued to press me. She pressed her niece and her husband to find this one Shadow, why even I still cannot understand.
You should have seen Atar; he was full of energy as he searched the regions that the other soldiers were too scared to venture into or had monsters like an Ursa Major resting there. He was determined to find her Shadow at all costs, just as my sister was determined to make sure Thrack wouldn't rise again. Their view on the fact that Thrack would rise to fight a fourth time was purely wrong as nothing, and I mean nothing, has ever survived my sister's Black Flames.
You wouldn't believe it though; after weeks of searching for the Shadow of Sweetie Belle we finally found her hiding somewhere in Evilville, the Shadow of Ponyville if you will. She was having fun with the Shadow Mark Crusaders, not terrorizing the citizens and destroying everything. Apple Poison and Wreakaloo were glad to hear that Bitter Belle would be joining them in class at the School of Shadows, along with their counterparts.
Be warned though, Bitter's form is the same as Sweetie's and yet she doesn't contain the power of Thrack either. She was glad to hear that she would be joining her friends and counterpart, but something honestly doesn't feel right. Darkstar claimed that she searched for this filly to be sure Thrack was dead and Atar seemed to make sure that he left no stone unturned while he looked.
Be sure to tell Celestia that the threat of Thrack returning is no longer a possibility and that she can rest easy knowing that the filly is going to be under watchful eyes. Also pass along to Sweetie that we have discovered her Shadow and that she will be meeting her when the train arrives to pick them up in a weeks time. Pass along my best to the Elements of Harmony, your sister, the Cutie Mark Crusaders, and the rulers of the Crystal Empire.
From your counterpart,
Princess Nightmare Moon of the Shadow Realm
Luna read over the letter for a second time to be sure the contents were authentic before making her way to the throne room of Canterlot, where her sister was currently watching over. The sun was up and she was supposed to be asleep, but thanks to the letter she knew her sister had to be told that Sweetie's Shadow had been found. Plus the fact that the monster Nightmare Moon had created was gone forever was something that would please her to no end.
When she arrived in the throne room she was surprised to find that her sister was signing papers and writing notes down on another sheet. She was preparing for her classes at the School of Shadows for when it was her turn and Luna was her watching over the world. She barely looked up as Luna entered, only giving her a nod of that meant she recognized that Luna was in the room at all.
"I have some news sister," Luna announced, "News that you might find interesting."
"I'm putting the finishing touches on my lesson plans Luna," Celestia said, penning something down before placing the parchment on top of a stack of papers, "Now, what is so important for my little sister to be up at this hour?"
"The discovery of Sweetie Belle's Shadow," Luna answered, showing the letter to her sister, "They discovered the filly, Bitter Belle, in the Shadow Ponyville not too long ago. She has already been admitted into the student list for the School of Shadows, taking classes with Sweetie I assume."
"So Thrack is dead at last then," Celestia commented, reading over the letter, "Thank Faust that she didn't survive to come back again. Now it seems that Nightmare has come concern that Bitter Belle might be some sort of a threat, but she doesn't say what though."
"I wouldn't worry about that too much right now sister," Luna said, causing her sister to raise an eyebrow, "The Shadow Mark Crusaders will be sure to keep an eye on her before she meets her counterpart and they go to class together. If they still have some of Thrack's abilities we can train them to use them for good and advert any disaster that might come with them. Besides, now we know that Sweetie's Shadow is alive, which means everything is back to normal at last."
"I hope so Luna," Celestia said, unsure of everything, "I agree with Nightmare; something strange is happening and Bitter Belle seems to be at the center of everything. But I agree that if anything is to happen it will occur at the School of Shadows. Now go to sleep and I'll send a letter along to Twilight."
"Alright sister," Luna yawned, "See you when the time is upon us again."
Celestia nodded and watched her sister exit the throne room, waiting until she was gone before summoning another parchment to begin her letter. She needed to make sure that Sweetie knew her Shadow was still alive and didn't do anything foolish. She knew that something was going to happen, but like Nightmare Moon she didn't know what that something was exactly.
-Ponyville-
"Girls, I have excellent news," Sweetie Belle said, tripping over a plank of the clubhouse as she got to the door, "Dang it, that piece of wood gets me every single time."
"What is it Sweetie?" Apple Bloom asked, curious as to what the commotion was this time as Scootaloo fixed the tire of her scooter.
"My Shadow's been found at last." Sweetie excitedly exclaimed, "She's been hiding with your Shadows all this time."
"Our Shadows?" Scootaloo asked, turning to face her friend, "I don't remember meeting them the last time we were at the School. What are their names?"
"Apple Poison, Wreakaloo, and Bitter Belle," Sweetie answered, stopping before her friends, "Not names I would expect, but its what they were named after all."
"Great, Wreakaloo," Scootaloo said, returning to her work, "I guess that means that she and I have more in common than most counterparts do."
"Don't think like that Scoots," Apple Bloom countered, "It just means that you two can tell tales and get to know each other like everypony else."
Sweetie smiled and raised a pawed hoof in front of her, wondering if her Shadow looked the same as she did. Werepony limbs, vampony fangs and wings, and strange draconic eyes. That was what Thrack had looked like in all of her terrible might and it was the form that Sweetie had been cursed to carry with her. She was still getting used to moving in this body, but after the defeat of the demon she had taken to the form more often than usual. She could still be a pony, but she felt that her strange form was a part of her and that she should embrace it, which she did most of the time.
True Rarity had nearly fainted the first time she had resumed the form and Applejack had nearly attacked her, but after explaining that she was willingly taking the form they had calmed down. Twilight wanted to run tests on her, but she refused and wanted the demon to die with her. No notes on her weaknesses and the like, which upset Twilight, but she eventually calmed down and accepted her decision.
Sweetie kept her smile and watched her friends as she wondered what their Shadows were like. One thing she knew for certain was that the Cutie Mark Crusaders and the Shadow Mark Crusaders would get along with each other just fine.