"Starlight," Twilight said, rifling through a box. "Can you give me a hoof organizing these artifacts?"
"Sure," Starlight said. They were in Twilight's castle. Starlight had carted over the artifacts from the School of Friendship, and now Twilight was using her empty shelf in the library to place them. "How are we organizing them?"
"I was thinking we'd organize them by use," Twilight said. Starlight cocked her head.
"What do they all do?" she asked.
Twilight raised a stone in the air with her magic. "This one grants three wishes," she said. She raised another one. "This one magnifies magic," she said. Starlight grinned a little.
"Have you been using it?" she asked.
"No way," Twilight said. "If you're already powerful, it can make your magic uncontrollable." Starlight absentmindedly smiled at the implication. Such a great artifact, but it wasn't being used? That is such a waste of magic! Good thing Starlight was already crafting a plan.
Starlight listened to Twilight talk about each artifact. There seemed to be something for everypony! Starlight didn't understand why Earth ponies didn't use the Flight Rope to give themselves Pegasus wings, or why unicorns didn't use the Strength Shoe to give themselves Earth pony strength. Or why unicorns didn't use both the Flight Rope and the Strength Shoe to make themselves Alicorns! Well, after tonight, one of these artifacts would be in use. The Magnify Stone seemed to be just the right thing for her. With that artifact, Starlight would be able to do absolutely everything! Who knows, maybe she could even make herself an Alicorn with magic! She would never get magic fatigue again! She could time travel consequence-free! She could make herself more powerful than Twilight! Her life would be perfect after she executed her plan. And all she had to do was one simple heist. This wasn't an evil plot. With this kind of power, she could help everypony! Who knows, maybe there wouldn't be any more trouble in Equestria. Who would need the Elements of Harmony and their carriers when Starlight could defeat every villain that came their way?
“I’m tired,” Twilight said. “I think I’ll take a…” She fell on a pile of books and started snoring. Starlight grinned. Her plan was going to go into motion even earlier than she thought!
Starlight found a blanket in the corner of the library and tucked Twilight in. Hopefully she would sleep even longer than Starlight needed, so she could impress her with her new powers.
Starlight stepped toward the shelf where the artifacts were organized. She took hold of the Magnify Stone with her magic. “Careful,” Twilight’s voice called out. “Artifacts…” Starlight froze. She looked back toward Twilight. She was still sleeping peacefully. Starlight let out her breath. She grabbed the stone with her magic and raised it into the air. Now was the tricky part. How to make it work? Starlight shook it around, bonked it on her horn (“Ow!” she said, making Twilight snore even louder), made strange incantations over it, everything she could think of and more. After a good fifteen minutes trying to make the rock work, she finally let go with her magic. The stone fell to the ground. Starlight winced, but Twilight stayed asleep. When she looked back towards the Magnify Stone, it was glowing! It was emanating with a purple glow, spreading outward. When the light touched Starlight’s cutie mark, the rock floated above her, enveloping her in a purple swirl. It raised her in the air, pulling out her magic and replacing her usual aquamarine color with a lavender the color of her coat. Starlight glanced back at her cutie mark, and gasped! It had changed! Instead of the purple star with teal decals, it was a blue star with silver decals! Her coat was slowly changing, too, turning a dark purple, even darker than Twilight’s mane. Starlight began to feel like a mare in somepony else’s body. She didn’t like it one bit. Maybe this was why Twilight didn’t want to use it. Maybe it...changed you. As soon as she had this thought, the swirl and the stone dropped her new body on the ground. Starlight didn’t even want to test out her new magic. She just wanted Twilight to wake up and tell her what had happened. Her eyelids closed gently, and she fell into a restless sleep.
Twilight woke up. Her bones were aching from the books giving her a hard position. She smiled when she saw that Starlight had put a blanket on her. Twilight was so proud of her pupil. She had turned from a cutie-mark stealing villain to a kind friend. That reminds me, Twilight thought, where is Starlight? Twilight looked around slowly. That was when she noticed the strange mare sleeping on the library floor. She slowly walked over to her. She looked familiar somehow, but Twilight knew she had never seen this unicorn before. That was when the mare’s eyes snapped open. To a familiar look, like she had some plan working its gears behind them. “Starlight?” The mare stood up, a desperate look in her eyes. Twilight noticed her cutie mark. It was the same as Starlight’s, but a completely different color. So was her coat. Her mane and tail were the same, she thought. And that look…
“Twilight?” the mare said. That was definitely Starlight’s voice. “It’s me.”
“What happened to you?” Twilight asked. This definitely wasn’t normal. She had never seen someone’s coat change, and the one time she had seen somepony’s cutie mark change, it hadn’t gone well.
The mare—Starlight—winced. “It’s a long story,” Starlight said. “Are you sure you want to hear it?”
“Definitely,” Twilight said. “Let’s fix this. Together.” Starlight smiled.
“Thanks,” Starlight said. “So, do you remember when we were organizing artifacts? You were telling me about the Magnify Stone—”
“You used it? Don’t tell me you used it!” Twilight said, fear in her eyes. “I told you it was dangerous!”
“I know now,” Starlight said. “So yeah, that’s how it started…”