Rarity was the most successful pony in Ponyville, or at least, many of the villagers said as much. It was an observation that Rarity found most flattering. Her Royal Highness, The Princess Twilight Sparkle enjoyed that observation considerably less.
But no matter how much the villagers' gossip grated Twilight, it was hard to deny the reasoning behind it. There wasn’t a high-end boutique in Equestria that didn’t have at least one Rarity dress, and they were widely recognized as the exemplars of their form. While Twilight’s palace was the largest home in Ponyville, Rarity’s was the most elegant, constructed of lines so flawless a pony felt they were standing inside a work of art. She was learned, she was beautiful, and she was rich, though you wouldn’t know it by how she acted. A tide of bits flowed into hooves, but just as quickly it flowed out again, given to charity or to support the many worthy merchants of Ponyville.
It wasn’t about the money, she would say. She created just to create. Better the bits go to somepony who would treasure them more. Colts and fillies looked up to her. Mares and stallions asked her advice when they were troubled. And she always had plenty of time for her five wonderful friends.
Until, one day, she rose from her bed and discovered a broken glass on the floor. It was the glass of water she kept by the bedside. She presumed she had knocked it over in her sleep. Her eyes flashed green, and it was mended.
Twilight cleared her throat.
Rarity’s head shot up. Her eyes were wide, and they needed a moment to refocus. Even once they had, she needed a moment to recover her composure. “Really, Twilight?” she asked. “Watching a mare sleep?”
Twilight stepped out into the center of Rarity’s bedroom. Her horn glowed, casting a pale light around the room. “How are you doing this?” Twilight demanded.
“You know more about magical theory than I do, Twilight. I’m sure you could reconstruct the spell yourself in—”
“All dark magic is powered by something,” Twilight’s voice was sharp, and her expression hard. “I didn’t believe it. I didn’t want to believe it. I told myself that it couldn't possibly be true, since your creations weren’t hurting anypony. Since they didn’t drain anything from the community. And yet here we are.”
Twilight’s throat tightened, and her voice rose in pitch. “What? Are you sacrificing animals? Are you sacrificing ponies? How are you doing it?”
Rarity didn’t answer right away. She licked her lips, and took a breath, and her expression calmed. Slowly, she climbed out of bed and stretched. “A designer never reveals her secrets.”
“Why!?” Twilight shouted. There was a tightness around her eyes, and her voice seemed like it might crack. “I could have helped you! We all could have helped you.”
“No, Twilight.” Rarity shook her head. “You could have gotten me to accept the world around me, and that would have been no help at all.”
“Fine.” Twilight sniffled. “Fine. If that’s the way it has to be. We helped Luna even when she wouldn’t accept it. And we’ll help you.” Twilight squared her shoulders. “I need you to come with me now. We’re going to Canterlot.”
“No.” Rarity turned a slow eye over Twilight. “We aren’t.”
“I can force you to come, if you make me.” The glow around her horn brightened. “I know what a dark wizard is capable of. I have the power to stop you.”
“Theoretically, yes,” Rarity said, words picking up. Her tone turned conversational, almost academic. “But all the power in the world is useless if you lack the will to use it. Evil prevails when good ponies do nothing and all that. There was a time and a place you could have stopped me, but you hesitated. And now it’s too late.”
“I’m sorry, Rarity. But you’re wrong.” Twilight’s horn shone, and she focused her attention on the unicorn before her.
Nothing happened. Twilight set her teeth, but she just couldn’t make the spell come. The pain was written all over her face. Rarity could see the conflict there, as something inside Twilight screamed that she could never turn her magic against her friend. Something inside her forbade it.
The light on her horn went out.
Then there was a green flash, and she was chained to the floor.
“You see, Twilight,” Rarity said, “the ideal version of you? The version that should be? She supports me. She’s the Princess of Friendship. How could she not understand?” The two mares were alone in the darkness. Twilight’s horn was unlit, as was Rarity’s. The room was pitch black.
Save, of course, for the faint glow from Rarity’s eyes. She looked right at Twilight. “And you become a little bit more like that mare every day, don’t you?”
“No.” Twilight’s eyes went wide, and breath came in quick pants. She strained in her chains, pulling as far away from Rarity as she could. “Rarity, listen to yourself! This isn’t who you are! You’re about to throw away anything you ever wanted just for some… some stupid toys and dresses!”
“They’re not toys, Twilight. They’re my children. They’re my visions.” She reached out to cup Twilight’s jaw with her hoof, and the glow behind her eyes brightened. “They’re the things beyond this world that yearn to exist and I am the only one who can make it so. They’re what gives my life meaning.”
“We’ll stop you! Celestia and Luna and all the girls.” Twilight spat the words, pulling her head far away from Rarity. “You won’t get away with this!”
“Maybe not,” Rarity whispered, “but know this, Princess. Though the Elements of Harmony, or Rainbow Power, or whatever other little miracle of friendship you conjure may drive this magic from my mind, it took no possession or compulsion for me to betray you. I will never love you as much as I love them.”
Rarity leaned in. Her eyes shone bright. Twilight felt herself changing.
“Yeah,” Twilight said. “I know.”
Then, with all the might and power of an alicorn princess, she headbutted Rarity.