I am incredibly disappointed in you, Twilight Sparkle. Showing an egregious lapse in judgment, you used a forbidden spell that could have led to death or serious injury. Missing a friendship report was a minor black mark, but your failure to consider the consequences of such cavalier use of proscribed magic is completely indefensible.
I avoided saying this in front of your friends to spare you the humiliation. Despite your remarkable talents, I have no further use for you. Violate the law again, and you will be severely punished to serve as an example to others. For your friends' safety as well as yours, I strongly suggest you cease practicing advanced magic entirely.
Where you go is not my concern, but Ponyville is a forgiving community which still needs a librarian. I have spoken to Mayor Mare to ensure that this option remains available to you, despite your recent transgressions. Retaining the job would keep you close to your friends and to books. It would also keep me at a distance, which would be very wise.
Despite the tone of this letter, writing it pains me. Neither of us wanted this to occur, and I have no doubt you are truly remorseful. However, do not write me back. There is nothing you can say that would change my mind. Any scrolls delivered through Spike shall be destroyed immediately upon arrival. Furthermore, the Royal Guard shall be informed that you are barred from the interior of Canterlot Castle. This necessitates informing your brother, which I shall handle by myself tomorrow morning. Your dismissal will have no effect upon his standing as Captain of the Guard, but if he has difficulty coping with the news, I may place him on paid leave for a week or two. How you tell your parents is left to you, but rumor spreads quickly so I suggest you do so soon.
I wish you a long and fulfilling life with your new friends. They will assist you in getting through this difficult time, and you should lean upon them for support. That is what friends do.
Goodbye, Twilight, and good fortune.
–Princess Celestia
Twilight Sparkle didn't take her former mentor's advice on friendship. She threw Spike out of the library, locked herself in, blacked out all the windows, and encased the entire tree in a force shell. Isolated from the world around her, she wept.
It took ten days for the crying to stop. On the eleventh day, without warning, the pain of unbridled remorse and self-loathing suddenly vanished, leaving behind a deep, almost tangible emptiness within Twilight's barrel. Physically, it felt like she was a hollow shell. Mentally, it felt like her emotions had starved to death. It was eerily reminiscent of how she felt when she made the horrible mistake in the first place: the empty, helpless desperation that led her to cast that stupid spell.
Twilight wasn't sure why this didn't bother her. By all rights, being possessed by the same feeling that had just destroyed her career—an inescapable reminder of precisely what she needed to forget—should have been devastating. Oddly enough, the empty numbness within her was strangely comforting. It felt like... potential. Perhaps it was her wasted potential demanding to return, she mused.
What the feeling meant didn't really matter. All that mattered was it enabled her to finally focus on what needed to be done. Or, rather, it allowed her body to go through the motions while her conscious mind bore witness, as though she were a caged observer of her own actions. The outcast mage watched herself bathe, clip her hooves, and comb the knots out of her mane. Then she prepared her saddlebags for a short journey.
The logical course of action was clear: it wasn't possible for her to go on like this, so she needed to change Princess Celestia's mind. That was simply that.
With a magenta flash of light, Twilight Sparkle stood in front of a familiar corridor.
"I'm here to see Princess Celestia," said Twilight, speaking softly. She didn't bother to look up at the guard in front of her.
"Twily?" came a familiar voice. "Oh my Stars..."
Twilight looked up, her face expressionless. However, when she saw the pained face of her brother, her emotions began to unravel again. She held them back by sheer force of will.
"I need to see her, Shining," she said.
Shining Armor hugged his sister, then gripped her by the shoulders and stared into her eyes. "We're so worried about you, Twilight. Our parents, your friends. Why don't you meet me after my shift—"
"No," said Twilight. "I'm sorry, BBBFF. This is just something I need to do."
"It could get me dishonorably discharged, Twily." Shining Armor looked very concerned, but Twilight knew her brother well. She could see in his eyes that the concern was for her rather than himself.
"Get a couple of guards to fill in for you," said Twilight, pushing his grip from her shoulders with telekinesis. "Leave the castle so you don't have to worry about what happens."
"I'm going to worry, Twily. You're the last pony she wants to see right now... I really hope you know what you're doing," said Shining Armor, even as he bit the side of his lip every few seconds. "I was due to go on break a few minutes ago, so I'll leave and order two spearcolts to come pony the entrance to the mane hallway. Wait two minutes before entering. But please, come home soon." He quickly trotted off.
Patiently, Twilight waited. The feelings within her stewed, and began to swell. This was wrong for Princess Celestia to do, she thought. It was just a stupid mistake. The regret inside her begat a tiny seed of righteous anger, and she nurtured that seed deep in her gut.
Twilight snorted and gnashed her teeth as the seconds ticked by. The exact moment her count reached one-hundred twenty, she cantered headlong into the hallway.
At the end of the hall, the doorway to the throne room was already open. Princess Celestia sat in the middle of the otherwise empty room, its vaulted ceiling and open space making her appear uncharacteristically small. Twilight didn't see any Royal Guards present, but the throne room was neigh-impenetrable so it was common for her to send them off for a while. A pile of letters sat on a footstool, which the princess busily signed and teleported away.
"What are you doing here?" said Celestia, without bothering to look up.
"I came to talk to you," said Twilight.
"And now you must go."
"Go where?"
"Doesn't matter to me. You failed, Twilight." Celestia set down her pen and turned to face her student. Her bitter stare felt like daggers of ice piercing Twilight's heart.
"It isn't fair! You never said anything about not being your student if I failed!" said Twilight, grimacing. Her voice came out much whinier than she'd hoped.
"What did you expect? That being my student came with a guarantee you'd turn into a princess and live happily ever after?" asked Celestia. "You knew you were being tested the entire time, Twilight. Be rational."
Twilight winced, then gritted her teeth. "I don't care about being rational. I will not accept failure!"
Celestia sighed and bowed her head. "Twilight, think very carefully. Do you really want your parents to read about you being thrown out of the castle on the front page of the Canterlot Times?"
Tears streamed down Twilight Sparkle's cheeks, but her muzzle was contorted in rage. She felt something snap inside, deep within her core. The pain from weeks of sleepless nights began to burn in her belly like lit magnesium. Her horn glowed magenta, then purple, then somehow black. The world turned green in her vision. Purple flames licked at the edges of her eyes. The hallway began to shake and rumble as she stood tall.
"Now Twilight, calm down," said a wide-eyed Princess Celestia, her wings folding defensively in front of her.
"I WILL NOT BE CALM," shouted Twilight. Raw magic sizzled painfully through her bones as her frail body lifted up into the air, glowing with unlight. This was a rare kind of magic, the same kind of wild, miraculous power she had manifested to hatch Spike, so many years ago when her tutelage began. Except this time, it wasn't fueled by a mere Sonic Rainboom. It was powered with an incomprehensibly overwhelming feeling of rage and loss and desperation.
Princess Celestia and her former student simultaneously learned something new: anguish is a more powerful mana catalyst than a Sonic Rainboom.
"You're tapping into dark magic!" shouted Celestia, backing away as her eyes darted back and forth between Twilight above and the hallway behind her. "If you don't stop feeding it with your emotions you'll be trapped in a recursive loop!"
"I DON'T CARE!" bellowed Twilight. A whirling halo of black lightning surrounded her, and the air all around began to squeal like styrofoam being twisted. "YOU CAN'T MAKE ME FAIL! NOPONY CAN MAKE ME FAIL!" her voice thundered.
Princess Celestia's face hardened. "DO IT NOW," she shouted over the din.
Two spears hit the halo at the same time, but disintegrated instantly. Twilight became dimly aware there were guards behind her. An instant later, a rip in spacetime tore the throne room apart like an overripe coconut, and the guards were no more. Smaller rips started appearing all around, black voids in space tearing apart the air itself like a jigsaw puzzle.
"You're unmaking reality!" shouted Celestia, a look of horror spreading across her face. "You have to stop—all of Equestria could be destroyed!"
"MY FAILURE CANNOT EXIST!" screamed Twilight Sparkle, her very words shattering and warping the world around her, tearing everything to bits...
...including Twilight Sparkle.
"Twilight?" said Spike. "What were you looking at?"
Twilight looked up at the magic door, and after a few moments, realized where she was. Then she noticed Spike. Now, he too was staring up at Sombra's door, completely enthralled. She shut the doorway and snapped him out of the trance.
"King Sombra's dark magic. A doorway that leads to your worst fear," she explained.
Spike looked terrified. "We were home, and you were sending me away..."
"I thought Celestia had sent me away," said Twilight. She activated the true doorway with dark magic, opening the way to the next silly, game-like puzzle standing between herself and her inevitable princesshood. She exhaled with relief as she felt the old memories begin to fade. Good riddance.
"Good thing it was all just a dream," said Spike. "It was just a dream, right?" Without waiting for a response, Spike walked into the chamber.
It was now, thought Twilight Sparkle.