The guards standing in front of the restricted section of the Canterlot Royal Archives were good ponies. They could be a little rough around the edges at times as guards sometimes had to be, and they were not above the occasional lustful thought as they eyed a mare passing by. But nothing that really qualified as darkness in their hearts. As such, they were completely under the effects of the shadow cloak worn by the unicorn mare that strolled toward them, completely unable to consciously perceive her presence. Their subconscious perceived her, just enough for them to find it unsurprising when the door they were supposed to be guarding opened for her, and she strolled right in past them.
Once inside, Midnight Oil hurriedly got to work. She lit a small candle, floating it in the air above her with her horn's magic while she started lifting books from the shelves on both sides of her, flipping one open before each eye and instantly memorizing page after page. She had done this trick many times before in less guarded libraries throughout Canterlot, but this time was different. She was on a time crunch, not only because of the risk of being caught, but also because of the urgency of the materials being made available to the other ponies of her kingdom. She didn't have time to look through every book, only those with promising titles. If the spine of the book didn't contain a synonym for 'dark' or one of its derivatives, she passed it by unopened. As promising as a 'Comparative Study on Various Magical Fireballs' looked in general, she had a very specific goal in mind.
Midnight had taken as many precautions as she could to make sure this raid went smoothly. One of which was dying her fur to match that of Princess Twilight Sparkle, right down to the cutie mark. The cloak covering where her wings would be would temporarily avoid that discrepancy from being visible, and it helped that her aura color coincidently matched that of the Princess of Friendship. The Princess herself should be unable to perceive her through the shadow cloak, if nopony pointed her out. One of her friends and fellow subject, Moonbeam, was surreptitiously scheduled as one of the guards for the archives tonight when the night guards took over, though if she didn't find what she needed by then it would be a problem of its own. A few devices in her saddlebags would tilt things further in her favor, one of which she took a moment to activate now. Lastly, the pair of bracers on her forehooves provided her a few tactical options in the event that things did get heated.
She had some initial success, finding a few works that managed to touch on the subject of interest, before a voice called out to her from the main pathway. "Excuse me, miss, you can't be here..." it began.
"Hmm?" she answered, turning sideways to let him get a look at her falsified flank mark. She quietly tensed. For the unicorn stallion that confronted her to have noticed her, he must have enough darkness in his heart to pierce the veil, or some other powerful magics active to break the deception. While they knew Princess Celestia herself had been able to create dark crystals as a demonstration, and thus clearly had the darkness needed without being consumed by evil, few other non-evil ponies had been able to see through it. Most were those like herself, ponies who had lived through horrific, traumatic experienced and left with a piece of them desperate to lash out at the cruel world that would let them suffer so.
"Oh, Princess Sparkle! I didn't expect to see you here today. Forgive me, I..." he started to turn away, and then suddenly snapped back to attention. "Imposter!" She had no idea what had given her away, but was already on her way around the corner. "Guards! There's a thief in the archives!"
A bubble of blue telekinetic force gripped Midnight for a moment, lifting her from the ground and immobilizing her for a moment, before a small dagger floated out of her pouch and popped it like a soap bubble, the runic markings on the blade flashing with light momentarily. The librarian was surprised for a moment, but began casting a spell, only to have the dagger fly out and tap him lightly on the horn, cancelling his spell. There was no aura of magic around it as it flew, but from her gestures it was clear Midnight was somehow directing it with a hoof.
Things got intense. The unicorn kept trying to cast, while aggressively approaching the somewhat smaller and weaker mare, and calling out for guards. It was a wonder they couldn't hear him, being as they were right outside the door. Meanwhile, the mare not only kept tapping his horn with that accursed blade that magically, if awkwardly, flew through the air despite being seemingly immune to magic otherwise, but she also kept drawing books off the shelves as she retreated, and flipping through them page by page as if desperately searching for something. He would think her choices of books random if not for the fact that he was a fast enough reader to catch the trend in the titles.
"You've really doomed yourself now, filly! There's no way we can let you go after reading so much on dark magics. They're forbidden for a reason, you know? When the guards catch you, you'll never see the light of day again!" he said, trying to intimidate her into making a mistake.
Midnight Oil grit her teeth a bit, deciding not to say anything. The mission was key, but after that they still had to live with these ponies, and that meant whatever she said now could come back to bite them someday.
With her harassment, the librarian had only the barest openings to cast, not enough for any true spells, and barely enough for any telekinesis. But he had learned that if he blocked with one hoof, he could slow the blade down a little longer, forcing it to go around his hoof to hit his horn and extending his time by a moment. So he decided to try and use that for a quick distraction. Right after one of the horn-taps, he lit up his horn and opened her saddlebags, dumping the contents before she could tap his horn again. A small rubber ball with holes in it dropped on one side of her, bouncing lightly, while a glass orb dropped from the other, shattering on the stone floor and cancelling an enchantment he hadn't realized he was being affected by until it vanished.
"Guards!" he called out loudly again, and this time they opened the door, coming to his aid.
There was just one problem, one he hadn't realized yet. "Hey, Forbidden Lore, what are you doing? You're going to have to clean up that mess, you know."
"Intruder!" he replied, pointing at Midnight Oil.
"What? Where!?" and soon they were off past Midnight, and looking around the corners beyond her.
Midnight smirked in amusement, but she didn't have time to waste. The librarian was smart enough to rip her cloak off next, she was sure. She knew she had reached the limits of what success she could achieve here, and quickly dumped a pile of books on the librarian as a distraction of her own before racing around a corner, pulling her blade back to her in the process.
The librarian was around the corner after her just in time to be hit by a translucent wave that disrupted his magic momentarily. But then, the intruder was gone. He spent another half hour searching for her to be sure, including a few magic tricks of his own, but she was gone. He thought she must have teleported away, but the disruptive wave had wiped out any lingering trace of the teleportation magic that might have allowed him to track her destination.
But she hadn't gotten away smoothly. The glass orb whose enchantment prevent sound from exiting its area of effect was destroyed. But perhaps more importantly, the little rubber ball would surely prove a vital clue to their intruder's identity.
[That's all I was able to get, my King. Will it be enough?] Midnight asked me.
[It will have to be. Most of this is going to be useless to us, at least here. I'm going to assume that using dark magic directly on the shadow creatures is counterproductive, so stuff like these mind control spells is right out, and the direct attack spells. I'm amused that someone worked out how to use shadow magic for TK, since you ponies normally do it with your ordinary 'love' magic. Shadow TK might be effective against the shadows, I'll have to try it at least once. Self-empowerment should work. These defenses are going to be questionable, but worth a try. Thank you Midnight,] I answered.
[Experimenting will be good, remember the idea is to burn off the dark power as quickly as you get it. Be aggressive, and try not to hold onto any,] she needlessly reminded me.
[Yeah, speaking of my ideas. Did you find a way to plant the bug?] I asked.
[The librarian found it for me, so mission accomplished I guess? I still don't get why you wanted me to leave that behind,] she wondered.
[It's politics. You wouldn't understand. And won't. Just trust me, especially when the time comes. Now I just hope they manage to put two and two together,] I replied.