The next morning Twilight woke up, and sat up in the bed. She stared around at the room as if trying to decide whether she was really still there, that it hadn't all just been a wonderful dream.
Cadance looked in from her room. "Morning, sleepy-head! Ready for some breakfast?"
"Uh huh!"
After a quick but solid breakfast served for them at the table near the windows, Cadance led Twilight out into the corridor and on a long, winding route through the palace. As they went, they passed numerous guards, all of whom came to attention smartly as they passed.
They turned a final corner and came face to face with a set of plain, gray doors, tall and wide, with no sign of doorknobs or any other means of opening them. As they approached, the doors swung open and Celestia herself stepped through. Behind her, the doors swung closed again.
"Good morning, Twilight! Ready to begin?"
"Yes, your Highness!" Twilight said. She moved to kneel respectfully.
"Twilight!" Celestia snapped. "Stand up straight! From now on you will neither kneel nor bow in my presence. I am your teacher, and you are my student. I want your full attention. No crouching, no crawling, no hesitation! And if you have a question, any question, you will ask it! Am I clearly understood?"
"But... what about in public? Everypony kneels to you!"
Celestia considered it. "When we are with others and it is socially required, it is permitted. When it's just the two of us, never! Understood?"
Twilight nodded. "Yes, your Majesty!"
"Thank you, Cadance," Celestia said to her. "I'll send for you when we're finished. Shall we say around lunchtime?"
Cadance nodded. "Highness." She smiled at Twilight, and then trotted off.
"Now then, my student," Celestia said. "Your first task is to get into the classroom. It's right through these doors behind me."
Twilight approached them, looked at them. "There's no doorknobs!"
"Very observant. What else do you observe?"
"They're... old?" Twilight said, puzzled. "They're... gray?"
"Three for three," Celestia agreed. "What else?"
Twilight thought for a moment, then shook her head. "I don't know! There isn't anything else!"
"But there is! Look more closely."
Twilight stared and stared, but couldn't see what Celestia meant.
"Do you see the crack shaped like a bird?" Celestia suggested gently.
There were cracks in the ancient, much-repainted wood, Twilight saw, but none that specifically looked like the one Celestia meant.
"Or the dent where someone tried to break in by kicking them?"
As hard as she looked, Twilight couldn't see what Celestia meant. Yet she was determined not to give up. She decided to be methodical about it, like one of her books had suggested. She started at the upper left corner of the door frame and moved her gaze steadily rightward until she hit the upper right corner. Then she worked her way back leftward. Back and forth she went, from one door to the other, steeling herself not to look at Celestia for another hint.
Celestia stood beside her, patient and unhurried, letting her search.
After a while, Twilight spoke up. "I... see a spot where the paint is chipped. And there's a rough bit, like there's a knothole under the paint. And a greasy spot. And a really wiggly crack, like a doubleyou with too many you's..."
Suddenly, she looked back to a spot in the upper left. There was a crack, actually two of them, two small arcs, that looked like a bird. And as her gaze swept onward she saw a rounded dent that might have been made by the edge of a metal shoe striking the door. And other details -- the more she looked, the more there were.
She dropped to the floor, trying to see underneath, but the door came down flush to the floor. Yet the bottom edge wasn't smooth, it had notches and places where the planks joined up.
She stepped closer, and saw that the surface of the paint was uneven, with small bumps and pits left by air bubbles. On a whim, she sniffed it. The wood smelt dry, a little musty. She put up a hoof and gently nudged the surface. The door juddered slightly, like it was loose on its hinges.
And then she put her eye to the very narrow gap between the doors, trying to peer between them.
Soundlessly, the doors swung open. Twilight had to hurriedly back out of the way to avoid being brained by them. She looked up at Celestia, who nodded.
"Very good, Twilight! This doorway is very special. It is called the Gateless Gate. It is proof against any force, any magic. It will only open to someone who has studied it closely, and knows it well enough to be able to distinguish it from any other door. Someone who is then able to see past it, and realize it isn't really a barrier at all."
She strode forward into the room beyond and Twilight hurried to keep up. Behind her, Twilight heard the doors swing closed, but she didn't pay attention to them because she was trying to figure out what she was seeing in front of her.
The room was gray. Not like fog, or smoke, or a cloudy sky. Just... gray, a single flat shade of gray all around her, with no lighter or darker spots, no signs of walls or ceiling, no features of any kind. She couldn't even really see the floor, even though she could feel it underhoof.
She looked behind her and couldn't even see where the doors had been.
Yet Celestia was still there, standing beside her, completely unworried and giving her time to take it all in.
"This room is called the Vault," Celestia said. "It was created a long time ago, when magic was sometimes used in... shall we say harmful ways. It is shielded from magic, so no spells can get in. But equally, no spells can get out, so I have re-purposed it as a training room. You can let off any spell you like in here, and it will harm no one."
Celestia came about so that she was facing Twilight.
"Now, I want you to do something important for me," she said. "I want you to think back to what happened at the entrance exam.
Twilight, at first eager to help, drew back at that. "I'm not sure I want to! It was... scary!"
"I know it was! You were channeling far more magic than you'd ever had access to, more than most unicorns ever have to manage. And since you weren't prepared for it, it started to get away from you."
"But... I turned my parents into plants!"
"And who turned them back again?" Before Twilight could reply, Celestia gave her a significant look. "You did, Twilight!" she said. "You could sense what was happening and you didn't like it, so you put things back the way they were before."
"I thought you undid everything!"
"I merely helped stabilize the magic. You decided what to do with it."
Twilight still looked doubtful, and more than a little frightened.
"Look at it like this," Celestia said. "You were standing next to the deep end of a pool. Someone bumped you, you tripped and fell in. You floundered around a bit, not being used to it. And then you climbed out. All I did was offer a steadying hoof to help you. And that is what I'm going to do here, so that you can learn to get used to it, a little bit at a time."
"Um," Twilight said, in a small voice. "Okay."
Celestia leaned close, touched her nose to Twilight's. Twilight could smell the Princess's breath. It smelled like caramels, of all things.
"Shut your eyes," she said gently.
Twilight did so.
"Can you feel me, here with you?"
"Yes."
"I'm right here, Twilight," Celestia said. "I'm not going anywhere. Now, think back to the examination, to what you told me about it. You were trying to hatch the dragon egg. You had tried every spell you knew, you felt like giving up. Then you heard and saw the explosion outside. It felt like one of your nightmares. It frightened you..."
And just like that, Twilight felt the blinding wash of magic energy flowing through her again, like electric fire, tingling and blazing. She tried opening her eyes. As before she could see nothing but the implacable white glare. It was like drowning in searing, actinic light. She felt terrified, wanted to stop it, to get away from it.
But she still felt Celestia's nose pressed against her own. And Celestia's horn brushed against hers, her mane cascaded around Twilight's face. The simple touches comforted her. She wasn't alone here.
And, she realized, the magic wasn't getting away from her this time. It was still blazingly bright, but she found her eyesight adjusting to it. And gradually she saw Celestia's smiling face materialize out of the glare.
Seeing that Twilight was comfortable now, Celestia drew back and looked around. Twilight did likewise. They were surrounded by the gleaming, blazing featureless energy. It was much like the gray room, only a thousand times brighter.
"I'm impressed, Twilight!" Celestia said. "Do you know how many times I had to kick that door before I realized how to get in? And how many tries it took me to be standing here, in the eye of my own magic, able to withstand it all without it crashing in on me?"
She looked at Twilight. "You have rare talent! Don't let anyone tell you otherwise. But this is only the beginning. You understand how to tame raw magic. Now you must learn to put it to use. Most unicorns only learn a few spells, which they use blindly, by rote. Your talent runs much deeper. You'll need to learn many different kinds of spells, understand what they all have in common, and then you'll be able to assemble spells yourself, so they do what you want them to do. And you'll also need to learn how to control the magic you can tap, letting just enough magic flow through the spells to make them happen." Celestia smiled at her. "Yes, it will take time, and there'll be some hard lessons to learn and a lot of difficult study. But I know you can do it, Twilight!"
"I will, Princess! I want to!" She looked around. "So... what do we do first?"
"Well, you found your way in here. Think you can find your way out?"
Twilight looked around. "Um. Where's the door?"
"Where do you want it to be?" Celestia asked with a sly look. "Remember how I made you look at the doors before, really look at them, until you could recognize them clearly, and distinguish them from any other doors? And then find them again when you need them?"
Twilight carefully turned in place, to where she thought the doors had been. And then she pictured them in her mind, remembering the cracks, the chips in the paint, the rough texture, the smell of it...
And before her the doors steadily appeared out of the glow, as if they had always been there.
She cautiously stepped towards them and they swung open for her. With Celestia accompanying her she stepped through. Behind her, the doors gently shut. And just like that, she was back in the corridor outside.
"Excellent, Twilight. A very good beginning!"
"Thanks!" Twilight smiled.
"But Twilight, I need you to promise me something."
"What?"
"You're still learning how to manage the magic you can channel. When you're in the Vault with me, it is safe to do so. We can control it together. I need you to promise me you won't try experimenting with it on your own. At least not until you've had a little more experience. We'll know when you're ready!"
"Yes, your Majesty!"
"And if you ever feel frightened, if you feel like it's getting away from you, I want you to find Cadance or me. We can help you."
"Thanks, your Majesty!"
"You're most welcome, Twilight. Well, we seem to be done much earlier than I expected! Let's take a break and do something together, just you and me. What would you like to do?"
"Can we visit the School library?"
"Why did I have a feeling you'd suggest that? Come along, then."