“This place is huge,” Starlight Glimmer remarked to herself, rather amazed as she turned another corner, discovering a corridor she had never seen before. Sometimes she wondered if the castle really was bigger on the inside, as Spike claimed it was. Then again, Spike was prone to hyperbole, and during this same conversation he had also recounted the time he became 'Lord of the Dragons', so relying completely on the authenticity of Spike's information would be comparable to entrusting a magical castle to a pony who had nearly caused the destruction of Equestria. Which is exactly what Princess Twilight had done. The Cutie Map had summoned Twilight and Rainbow Dash to some remote location, far from Ponyville. Now, Twilight could have left any pony in charge of the castle. Any of her friends would have been far better choices. She could have even left Spike. But did she do any of these things? No. Instead, she left Starlight alone in the castle, with free roam and but one task to complete; read a book. Though she could normally accomplish this with ease, she had grown tired of the usual selection. Although Twilight's library was vast, everything seemed to be more of same. Starlight skimmed the shelves every now and then, whenever she had time to spare, and while there had been a few worthwhile reads, there was a multitude of generic, bland, and frankly, irrelevant books that greatly outnumbered the quality few. So here she was, roaming the halls, hoping to discover something to read. She had already found several rooms that had books randomly scattered, as if the library could not contain even one book more. Unfortunately, all of these were just as enticing as the ones in the main library, if not less so. Finally, she discovered something that piqued her interest. Only this was not a book. As she had gone to open the door to what she assumed would be yet another empty room, she faltered. The door knob would not budge. It was locked.

Starlight had yet to encounter a locked door in the castle, even for the personal quarters of the princess herself. What could it possibly be, that Twilight either valued or feared enough to keep behind locked doors. She did not have time to ponder this, as a voice echoed down the hall. Twilight.
“Starlight, we're back!” There was a pause. “
Starlight? Hello?” Suddenly, there was a flash directly in front of Starlight, startling her and causing her to stumble backwards. She immediately recognized the flash and the sound that accompanied it. Teleportation magic. Twilight appeared before her instantaneously.
“There you are, Starlight. How have you been?” Although Twilight was doing nothing out of the ordinary, Starlight thought she detected a hint of menace in her voice. Of course, it was most likely her imagination. But what about the door? Had Twilight not noticed that she was standing directly in front of the only locked door in the castle? Despite her reservations, Starlight couldn't help but think that this could not possibly be a coincidence. It appeared that Twilight was attempting to distract her, and she could not let that happen.
“Oh, hey Twi! How was your trip?” Twilight then launched into a tirade on her latest adventure, excessively describing every detail, no matter how small. Yep, Starlight noted mentally, involuntarily rolling her eyes, same old Twilight. After a great deal of babbling, she finally ceased. Unfortunately, the question she then asked caused Starlight to desire a return to the discussion of Twilight's journey, however dull it may have been.
“So, what book did you read?”



Starlight stammered nervously, unsure of how to go about this. If she was cautious, she was confident that she could talk and fib her way out of the situation. On the other hand, the nagging urge to discover what was inside that room was surprisingly intense. “Well, you see, I didn't really get around to that. I searched the bookshelves in your library, but nothing held my interest. So here I was, looking to find something to read, when you returned. Do you have any recommendations?” The indignation on Twilight's face was clear, though she attempted to mask it. “Oh, okay. Personally, I recommend that you read Mythical Creatures: The Complete Anthology, by Star Swirl the Bearded. Or if you have already read that... Hold on.” Twilight paused, glancing behind her at the locked door. “Actually, let me get that for you,” And with another flash of purple light, she was gone. It was clear that Twilight was onto her. Starlight could only imagine what she was actually doing. Maybe she was readying an imprisonment spell, locking Starlight in a dark cell beneath the castle, never again to see the light of day. The most she could hope for is that the princess would simply wipe her memory of this altercation. There she went again, leaping to horrible conclusions that would sound completely outrageous to any pony capable of utilizing logic. As she thought about it more, she realized that all of these sounded frighteningly akin to what the old Starlight would do. Her self-examination was abruptly halted when Twilight reappeared, a thick volume resting on her outstretched hoof. Starlight's horn ignited, levitation magic transporting the book to her back.
“Thanks, Twilight. I don't know what I'd do without you.”
“That's what I'm here for. You know what, Fluttershy is having a tea party at her cottage in a few. We should be on our way. Let's go!”
Starlight immediately felt the tingling sensation that she associated with teleportation magic. As soon as she felt it, it was already gone, leaving her directly outside the castle with Twilight. Starlight shuddered. Though she used it whenever it was absolutely necessary, Starlight had never cared for teleportation. “You said we still have a few minutes, let's just enjoy the walk.” The look on Twilight's face showed that she felt the same way, and she quickly agreed. And so, they began the brief trek to the cottage, both with much to say, but neither vocalizing any of it.

---

The party was enjoyable, though it seemed to drag on forever. Starlight knew she was still getting the hang of friendship, and every pony else seemed to enjoy themselves all the while, but the pleasure quickly morphed to pure awkwardness and tension for Starlight, for no particular reason. Maybe it was the fact that she stuck out like a sore thumb, being the only past super villain in a room with a close-knit group of friends who seemed to do no wrong. Or maybe it was because she had stumbled onto the one thing that remained untouchable in the castle of the princess of friendship, only to be caught in the act. Regardless, the party was over now, and both Spike and Twilight had retired to their rooms, leaving Starlight with the opportunity to further explore. She found her way back to the obstructed door easily, shining light on the door with her horn in the otherwise dark corridor. She began to charge a blast to break the knob, but hesitated first. Since her turn to this path of redemption, she had not used destruction magic. While her intent wasn't quite malicious, it was a decision that had some symbolic meaning behind it. It was not as simple as it appeared. In the end, her thirst for discovery overpowered her qualms. She was actually mildly surprised at how swiftly she had made her decision, how quickly the knob disappeared, leaving a small patch of ash on the surrounding area. The door swung loosely, and within seconds Starlight was in the interior. Although it was dark, there was a lone object placed on a pedestal in the center of the room that seemed to glow dimly, lighting the area surrounding it. As she neared it, she could see that it was a book. But before she could further examine it, a voice came from behind her, a voice that sent chills up her spine.

“Starlight?”
It was Twilight. She was clearly no longer trying to play innocent, her usually lighthearted tone replaced with something far more grave.
“What is it, Twilight?” Starlight asked in a similar voice. “What are you hiding?”
“It's not that simple. I thought I could trust you now. I didn't think you would respond to my allowing you to live here by zapping holes in my doors!”
Twilight was trying to change the subject. That was not going to happen.
“What is in that book?”
“You had my whole library to choose from! You have free roam of the entire castle, but no, that was not clearly not enough for you. You had to find the one locked door, and break in.”
“You never said I was not allowed in here.”
Twilight's fury momentarily dissipated, replaced with an incredulous expression, as if Starlight had just suggested they burn the library of Canterlot.
“Starlight, I consider you to be one of the most logical ponies I know.” Twilight said in a quieter voice again, “Why the hay would I deliberately lock this one door, and none of the others, if there were not something that I wanted to remain hidden.”
“But why does it need to stay hidden?”
“Some things are just better that way.”
“Twilight you aren't making any sense!” Starlight nearly screamed out of frustration. She tried to calm down, realizing that she was probably jeopardizing her relationship with Twilight with every word she uttered. There was a moment of silence.
“Sorry. I didn't mean to yell, it's just you aren't telling me anything.”
Twilight blushed. “You're right. I'm sorry too.”
“But what is it?”
“I don't know,” Twilight answered, her expression unreadable.
“What do you mean, you don't know? How could you not know?”
“She never told me.”
“Who?”
“Princess Celestia. When I got this castle, she delivered it to me personally. She said that she needed to keep it somewhere that is truly safe. She thinks her security is compromised, and until she figures it out, she just wanted to keep it here.”
“So you, Princess Twilight, eager to assimilate any knowledge you can get your hands on, have never even peeked at what's in there.”
“I'll admit, it was hard at first, but I had actually forgotten about it until earlier today. The important thing is, did you ever look at it?”
“I didn't have the chance to,” Starlight said truthfully.
“Good. Celestia made it clear that keeping anyone from reading it was imperative.”
Starlight shook her head at this, “Then why didn't you create a magical barrier as well. I mean, a physical lock isn't enough to protect something like this.”
Twilight smiled faintly. Good. Starlight's attempt to inject some lightheartedness in this otherwise somber conversation seemed to be working.
“That's a good idea, Starlight. I'll do that now.” They exited the room, Twilight placing a semi-transparent obstruction in front of the door, sealing it closed simultaneously.
“Well, this has been one eventful day. I should get some rest. See you in the morning, Twi.”
“As long as you don't go blowing anything else up, Starlight.” She began to feel offended, but a quick glance at Twilight revealed that she was making a joke. They said their farewells, and were both in bed within the minute.

---

No matter how much tossing and turning she did, Starlight found she was unable to sleep. She couldn't help but wonder what that mystical book contained. What knowledge could Celestia need to guard to this extent. This whole time, Starlight had assumed it was something of Twilight's, something personal. Maybe that was why she was so eager to discover it, as she did not know the princess as well as most ponies thought she did. Though they lived in the same castle, Twilight seemed to subconsciously avoid her. Not that she could be blamed, she had every reason to. But still, Spike was really the only one she interacted with on a regular basis. She was trying to change, but did ponies still view her as a monster? Unfortunately, that was still more knowledge she would most likely never attain. As Starlight's eyelids slowly drooped, her thoughts were filled with forbidden knowledge.