Twilight Sparkle stepped into the cave. She had told her friends to stay outside, so they wouldn't be hurt. She knew many complicated spells that could help her if she was in trouble. After all, they had been on this quest for weeks, and Twilight would die if Pinkie Pie sang one more song. This had to be it.
She expected a monster gaurding some sort of powerful artifact. But instead, she saw a pool. It was clear, with black moss around the edges. The room was extremely hot, like a sauna, and the pool bubbled. It called out to the lavender alicorn, saying, "Take a short swim, pony. Take a dip. What harm could possibly befall you, for bathing? You haven't had a bath in days." Twilight wondered why she would possibly step into the water, but eventually her instincts won. She trotted in.
The water was scalding hot. Twilight tried hard to scream, but no sound came out of her. It hurt too much. She thrashed violently around, but the burning liquid had already clamed the poor pony princess. She was changing.
It eventually stopped hurting, so she stepped out of the now glassy pond. She began to notice the changes the pool had made. Her once lavander coat was now a deep purple, her cutie mark being a red star with five white ones surrounding it. Her wings were huge, leathery, and bat-like. Her eyes were green and red, with purple smoke trailing out of them. Twilight's mane and tail were now jet black, with thin dark and light red streaks. It flowed magically, just like Celestia and Luna's glorious, ethereal manes. Long fangs stuck out from her mouth, a curved horn was in place of her purple one, and the transformation was complete. She called, "I am Midnight Sparkle, queen of Equestria, and I will take back what is mine!"
"Tw-Twilight? I-Is that you?" said Spike. Rarity added.
" You've certainly changed a bit, darling."
"Yeah," said Rainbow Dash, " You look 20% more..."
"Powerful?" She said in a commanding voice. "Oh, you simple foals. I wanted this all along. You and your pathetic princesses should have seen this coming a mile away. I am your queen, and you will bow to me!" She broke out in an evil laugh King Sombra would have been pround of. Then Fluttershy said,
"Twilight, don't do this, please..."
"Twilight is gone, slave! For I am Queen Midnight Sparkle, and all of Equestria shall tremble at my hooves! First, the Crystal Empire! Then, we take Canterlot! After that, Yakayakistan and Griffonstone!" She was now drunk with insanity, crazed with thoughts of slavery, wealth, and power.
"But first, I suppose I should see how powerful I truly am. After all," Midnight remarked, "I have followed the light for so long, I am not entirely sure I will be able to conquer Equestria without some practice in dark magic." She then noticed her friends slipping away.
"Where do you think you're going?" She trapped her former friends in a black telekinetic grasp.
"Um, nowhere at all! Nope! Totally not trying to escape the new cray cray Twilight or warn somepony or anything! Are you crazy?" said Pinkie Pie.
"Well, you could at least try to not give us away!" yelled Rainbow Dash.
"Oh, really now? Trying to escape? Trying to warn somepony? Well, that just won't do. That just won't do at all. After all," she cooed, "I need a few... Test subjects, to practice my new dark magic on. And you six, you are the perfect guinea pigs."
"Well, we're screwed, " stated Applejack, blunt as always.
"Now, for my first practice run..." She channed the new dark magic within her. Princess Celestia had shown her how before, so she knew how to do it already. Her horn lit up in purple, green, and black circles. The thick, purple smoke trailing out of her eyes grew thicker. Jet black obsidian erupted from the snow, forming the bars of a cage, looping and fusing together at the top. Midnight Sparkle stepped back to admire her handiwork. "Not bad. Not bad at all, Midnight," Midnight teleported five ponies and a dragon into the cage, "Now, for the real fun to begin."
For hours, she tested new spells. She made her former friends change form, writhe in agony, and forget about their loved ones, before erasing the damage she caused, until Midnight Sparkle finally stopped.
"Why would ya do this, Twi? Why?" cried Applejack.
"I needed the practice. Now," she began charging up her horn, "I need a way to force ponies to obey me. Not erasing their memories or brainwashing them, that is too easy. No, I will control them completely, force them to obey me... Against their will. Their bodies will follow my every command, but their minds will stay intact."
"W-Why is that necessary?" asked Fluttershy.
"It is far more fun that way. Now, to test it on you!" With a flash of her horn, she cast her evil spell. The ponies and dragon she casted it on's eyes grew green and red, before returning to normal. They slowly regained consciousness.
"What happened...? Wha...? Huh...?" Was the unanimous response of the six friends.
"Let's see if that worked... Applejack?"
"Yes, Yer Majesty?" The words were forced out of her mouth. Applejack tried to say something, anything else, but she failed.
"Tell a lie."
The others gasped. If the spell Midnight Sparkle casted really did work, this would make Applejack, the Element of Honesty herself, fib. Applejack tried to say "No can do, sugarcube." but her lips betrayed her.
"Ah hate apples."
Midnight grinned an evil grin. "It worked! Applejack, start using proper grammar. That has always bothered me, even when you were my friend. All of you, you are loyal only to me. You will never betray me, and always do what I say, when I say it. Do you understand, my little slaves?"
"Yes, Your Majesty," they droned.
"Good. Now, to the Crystal Empire!"