"Hey, um... can I ask a question?"
The twin dark mages leading the small party of foals down the main hall towards the spiral staircase that led to the second and third floors simultaneously turned to the curious lavender filly who'd just spoken. Twilight, who found herself intimidated at their sudden silent gaze, had to find her voice again but continued on nonetheless with the question that was bothering her. Starlight and Firebrand looked over her as well, their looks less unnerving but no less curious.
"You, uh... you said before that Aeon believed everything would turn out okay with the thestrals in the end," she began, trying and failing to look the twins in the eye as she spoke, "that implies that she knew we were in Nightshade, right? Did she see everything you both saw?"
The Gemini Twins turned to each other for a moment to have what looked to Twilight like another silent conversation. To Twilight's relief, the awkward silence that followed didn't last long, and the two were quick to respond.
"Our Mistress... did not witness your exploits... through our eyes," said Castor.
"She has gone past the Celestial Barrier... where the magic that would require such a feat... cannot reach," finished Pollux, "we can, however... continue to communicate... through simple Telepathy... neither the Barrier... nor the distance... are an issue for us."
"So you two are basically spies," Starlight pointed out, "I mean, if that's not what a spy does, then what is?" she turned to Twilight, "right? I'm right, aren't I?"
"Call us what you will," Castor replied in a dull but oddly flippant tone, "there are no secrets... between us and our Mistress."
"Our eyes and ears... are hers to do with as she sees fit," Pollux agreed.
Evidently feeling they'd made their point, the twins returned their attention to the path ahead. It was clear they were done with the conversation, but neither Twilight nor Starlight was satisfied with just that. For Starlight's part, the filly couldn't help but frown at the blind devotion they had to Aeon.
If we hang around that mare long enough, are we gonna end up like them? Like obedient little dogs, wagging their tails at every word she says?
The thought of it made her shiver slightly.
"Yeah, fat chance..." she muttered under her breath.
Twilight heard Starlight, being right next to her, but the only response she gave was a flick of the ear. She had other things on her mind and hadn't yet asked what she wanted to ask. Even without context, the lavender filly got the feeling she knew what Starlight was referring to, and if she was right, she could understand where the other filly was coming from, but...
"So... so if she knows what happened," Twilight continued tentatively. This time it was only Castor that turned to listen, but that was enough for Twilight to keep speaking, "...if she knows about what happened with the manticore... with Tenebrae... w-what does she think? Does she know what happened? O-Or why I—"
“Flight-or-fight response,” Castor explained, “a miracle… shaped by your affinity… and triggered by your survival instincts… nothing more,” as she spoke her next words, the mare smiled, though it was almost imperceptible, “I assure you, Twilight Sparkle... our Mistress is quite pleased… at this development.”
Twilight blinked in surprise.
"She... she is?" the filly asked, not quite sure how to feel about the response, "b-but I killed the manticore! I almost caused an incident with the thestrals!"
"They weren't too happy that Twilight offed their pet," Starlight chimed in with a sour frown, "that was kind of the whole reason we were arrested."
Firebrand, who'd been listening quietly up to that point, opened his mouth to say something, but Pollux cut him off before he could get the chance.
"The end result of your actions... doesn't matter to our Mistress," Pollux replied. She finally turned to stare into Twilight's eyes—much to the filly's discomfort, "what's important... is the experience you've gained... that feeling... that raw emotion and immense power coursing through you... remember it well, Twilight Sparkle."
But the filly didn't really want to remember it, she didn't want to remember any of it if she could help it. The look on her face must've said as much because now both twins turned to her before glancing at each other with small frowns. After a brief pause, Castor and Pollux seemed to lose interest and focused their eyes forward, but not before both spoke to Twilight one last time.
"Emotion plays an integral part... in the casting of Dark Magic, Twilight Sparkle... more so than almost any other branch of magic," she gave one last glance Twilight's way, "if you wish to master Dark Magic... if you want to avoid losing control... then learn to master your emotions."
"Our Mistress sees great promise in you... both you and Starlight Glimmer," Pollux continued, "she desires to cultivate that potential... and once honed, together your power will bring great change... to this wretched wasteland... this is our Mistress's ultimate wish... so please, do not disappoint her."
Though the flatness of their tone hadn't changed, both Twilight and Starlight could still feel some kind of negativity rolling off the twins, and Starlight, in particular, didn't miss the veiled threat in Pollux's 'plea'. The words of the Gemini twins were enough to quiet the fillies, and they all continued up the spiral staircase in silence—Twilight and Starlight's mouths shut, but their minds preoccupied with the implications of what Pollux had said. Twilight almost didn't notice when the twins halted their advance once they'd all reached the second floor. As Starlight stopped the other filly from bumping into Castor, Pollux turned to Firebrand, speaking loud enough for everypony to hear.
"This is where we are meant to part ways... with the others," she announced, "you and I... will go to see the one who will guide you... during your stay on the surface... come, little Firebrand..."
Without another word and without waiting for the thestral colt to reply, the diminutive mare started off down the mostly empty hall towards a destination unknown to the two fillies. Firebrand lagged behind for a moment, sputtering in confusion. He turned to the remaining three but received no help or explanation from any of them.
"What are you doing?" Starlight gestured down the hall with an impatient grimace, "she's gonna leave you behind!"
"You should probably just follow along," Twilight said with a small but sympathetic smile, "that's what we've had to do pretty much since we got here. You'll get used to it... probably."
"Well, b-but... I mean," the colt turned to Castor with a bemused and slightly pleading expression, "who am I gonna meet? If it's not Aeon, then—"
"Her name is Cheshire," Castor replied, "a retired Defender... she will see to your training... and your lodgings... go on... you're falling behind, little Firebrand," she turned to Twilight and Starlight, "we should be going as well... though night has fallen... your day is not yet over..."
Like her sister before her, the sleepy-eyed mare turned away and began moving without another word, though instead of further down the hall, she started making her way up the staircase to the third floor. Both Twilight and Starlight began to follow but stopped at the sound of Firebrand calling out to them. Both fillies turned, Twilight with a look of curiosity and Starlight with irritation etched into every part of her expression.
"Um... look, I..." the colt began. His eyes fell on Starlight, who's frown deepened. He winced and looked away, but continued on despite the glare, "...I'm sorry, alright? I didn't know you two had it that bad. I didn't mean to be insensitive, I just..." he glanced back toward Starlight and Twilight, but quickly looked away again before turning around, "n-nevermind, that's all I wanted to say... I'll... see you around, maybe."
And with that, he took off after Pollux, who'd already made it quite a distance, but was still in sight. Both fillies watched him go for a moment, but it wasn't long before Starlight followed after Castor, snorting in annoyance as she made her way upstairs.
"I'll be happy if I never see him again," she muttered loud enough for Twilight to hear, "the wimp can go die in the wastes for all I care."
Twilight gave Starlight a disapproving frown at the harsh comment. She found it a little unfair and just a touch unnecessary but said nothing in response as she followed behind. It wasn't worth arguing over she decided, and besides that, there was something else on her mind—namely what Castor had said about their day not being over. Unable to let that go, she asked about it once they'd caught up to the cloaked mare.
"So what did you mean by that?" Twilight asked as the small group made their way back to the library, "what else do we have left to do?"
"Yeah, I'm exhausted," Starlight complained, "can't we just call it a night and go to bed?"
It was true; the day's events had occupied much of their energy and attention, but now that their ordeal was more or less over, that energy was spent and both Twilight and Starlight couldn't help but focus more on their sore bodies and weary minds. They needed sleep, and badly, but to their disappointment and Starlight's frustration, Castor merely shook her head at the notion.
"Not yet... there is more for you to do... an agreement you must uphold..." she said in a dull but solemn tone, "a chance meeting... a mare in need of help... she waits for you in the library even now."
"A mare?" Starlight replied, frowning in bemusement, "what mare? What are you—"
Twilight's sharp and sudden gasp cut her off and the pale pink filly turned to see a look of both realization and guilt on her companion's face.
"Fleur!" she cried, "oh, Celestia, I completely forgot about her!"
"Who?" Starlight asked again, more baffled than before. It took a second, but after a bit of thought, she groaned and slapped a hoof to her face, "oh, right... her. You're telling me she's still there waiting for us? Why? And how do you even..." she paused and gave Castor a flat, not-at-all amused look, "right, you two have literally been shadowing us all day apparently."
"A job given to me by my Mistress... and one I must continue for the time being," Castor replied, with a single nod, towards Starlight, "Mistress Aeon wishes to ascertain... the reason behind that mare's suspicious behavior... to that end, my sister and I... will accompany you two as we have been... while you fulfill Fleur's request."
Starlight attempted to protest, but her pleas and outrage went unheeded by the mare. Twilight, on the other hoof—while not at all pleased that they were being used—was much more okay with the idea, given that she'd been the one to agree to help Fleur. While she hadn't exactly made a promise, she would've felt terrible if she'd missed the mare altogether. She already felt bad enough as it was, so when Starlight finally threw open the doors of the library and they all stepped inside to see Fleur waiting at one of the many empty tables near the back, Twilight was somewhat relieved. From the sharp gasp and shocked, panicky look on her face at the sight of the small group, Fleur clearly hadn't expected anypony to come waltzing right into the library so late at night. Starlight didn't miss that, and narrowed her eyes, feeling already that something was off.
"Ah! You are—" the startled mare began, rising from the desk she sat at so abruptly that she nearly knocked over her chair. She paused for a moment, terrified, then squinted at the two fillies trotting into the library and sighed quietly in relief a moment later, "—oh, goodness, I thought—but no... you are Twilight Sparkle and... Starlight Shimmer, yes?"
"Glimmer," Starlight grumpily corrected as she neared the table, "Starlight Glimmer, and yes, we're here despite how late it is. Question is why are you still here?"
As Starlight spoke, both fillies moved to seat themselves at the table Fleur sat at just as they'd done earlier that morning. Castor had once again melted into Twilight's shadow before she and Starlight entered the library and said filly was trying not to think about how uncomfortable it made her now that she knew the mare was there watching and reporting everything the two said and did.
"Oh, w-well..." Fleur frowned as she eased herself back into her chair, "it is a very funny thing, you see... I waited for you two for some time, but you did not show so I returned to my room in the tower," she shook her head and her frown deepened slightly, "but when I returned, I found a letter address to me on my bedside stand."
"A letter?" Twilight asked, now wearing a bewildered frown of her own. She and Starlight glanced at each other from across the table before looking back over to Fleur, "what letter? What did it say?"
"The letter... it mentioned the two fillies I was waiting for would be returning to the library just past midnight and to wait for them here," she eyed the other two sitting at the table with no small amount of bemusement and suspicion, "it could not have referred to anypony else but you, and yet from your reaction I take it you two did not know about this letter?"
"No!" Twilight was quick to point out, "I—we... I'm sorry, Fleur, but a lot happened today and we both kind of... completely forgot about meeting you here."
"Yeah, we didn't really have any time to send you any kind of letter," Starlight said. She leaned forward and propped her head up on one hoof, moreso out of sheer exhaustion than boredom or disinterest, "don't know who sent it, but I bet you it was one of Aeon's lackeys," at Fleur's look of shock, Starlight rolled her eyes, "look, I don't know that for sure okay? And no, we didn't tell anypony about the meeting, like Twilight said, we had other things to worry about."
"I... I see..." Fleur replied after a few seconds of thoughtful silence, "well... whether it was somepony associated with Aeon or no, this is still rather troubling."
"I guess so," Starlight said with a loud yawn, "but frankly I'm too tired to care and I'd really rather be back in bed."
Twilight, for her part, was fighting just as hard as Starlight to stay awake but made more of an effort to stay invested. Fueled by her anxiety of what had come before and what would come next, the filly pushed her weariness to the back of her mind and pressed on. She wondered whether or not the twins had somehow managed to sneak the letter into Fleur's room at some point, but chose not to mention them given that one of them was listening in and most likely wouldn't approve.
Starlight also had an idea of who it might've been of course, but—like Twilight—she wasn't going to say anything while that suspect was present. Both fillies remained silent on the subject and Twilight instead settled for moving the conversation along to where it needed to go. Neither said as much out loud, but both Twilight and Starlight agreed wholeheartedly; The faster they got this over with, the faster they could get some well deserved and much-needed sleep.
"Well, I don't think we're gonna find out just sitting here," Twilight said aloud, "but for now, why don't we just focus on what you wanted us to help you with?"
Fleur's remained quiet for another few seconds longer, her eyes narrowing slightly. It was clear to Twilight and Starlight that she wanted to ask more questions about what happened to them and wasn't entirely convinced that the two weren't involved, but she ultimately let it go with a small sigh and a slight shake of her head before rising from the table again.
"Perhaps it would be better to discuss this another day," she decided, "it is very late and you are both clearly exhausted from whatever ordeal you've endured. I am not so cruel as to force two fillies to accompany me when they so desperately need rest."
"That's fine with me," came Starlight's immediate and enthusiastic reply, "honestly, I think that's the best decision anypony's made all day."
"A-Are you sure?" Twilight asked in a markedly less enthusiastic tone. She turned slightly and cast a furtive and inconspicuous glance below the table, "I mean, I still feel bad that we made you wait so long... could you at least tell us what you wanted us to help with since we're here?"
It wasn't a complete lie—at least not on Twilight's part—and she hated to do it, but something told Twilight it would be a bad idea to end the conversation here without learning anything. She could practically feel Castor's unseen gaze burning a hole in the back of her head despite the mare being nothing more than a shadow. Unfortunately, it seemed like Fleur too was starting to realize that something was off.
"I am sorry," Fleur replied with an apologetic smile towards Twilight, "though I do not intend to drag you and your sister into any more trouble than you may have already gone through, this is still a rather sensitive matter and I would rather the wrong creatures not find out about it," she gave a humble bow of her head and began trotting away from the table towards the staircase that led to the living quarters below the library, "I will come and find you two again soon when I have the chance. I hope you will still be willing to help me then but for now, I bid you two bonne nuit."
Twilight watched the mare as she made her way downstairs and once she was out of sight, the filly turned to see Starlight already out of her seat. She crouched down into a languid, cat-like stretch before moving around the table to where Twilight was.
"Welp, that's that I guess," she practically chirped, "least we can finally get some—"
This is... quite an unwelcome development...
Before Starlight could finish, Castor revealed herself, stretching, twisting and morphing from a formless black mass into the cloaked unicorn mare that had been escorting the fillies. Just as Twilight had feared, she didn't look happy. That wasn't to say she looked upset or had any kind of actual expression aside from her normal sleepy stoicism, but even without visibly showing it, Twilight could still feel the irritation coming off the mare in waves. Twilight was ready to make an excuse, but Castor ignored her and turned her attention to the winding staircase.
"It seems... a change of plans is in order..." she said, speaking more to herself than Twilight or Starlight, "Mistress Aeon... will not be happy to hear of this..."
"Well, I mean, of course she's gonna be suspicious if she gets some anonymous letter about something that was supposed to be a secret," Starlight pointed out with another poorly stifled yawn, "I'd be pretty suspicious too."
Twilight couldn't help but agree, though she didn't say anything aloud.
"Well... at least we can try again," Twilight reasoned, "I still want to help her... and I'm also curious about what she wants us to do, but... um..." she paused tentatively, looking in Castor's direction. The mare, in turn, stared at her expectantly. Twilight opened her mouth to continue, closed it, then opened it again, "so... did you or your sister send the letter then?"
"No."
Twilight blinked and turned to Starlight, both of them sharing a look of slight surprise. They both turned back to Castor as she elaborated.
"My sister and I... we were under orders from our Mistress to watch over you... and we never once left either of you alone," she looked back over to the distant spiral staircase, "whoever sent that letter to Fleur de Lis... is an outlier... a creature whose interference warrants further investigation..."
"But you already knew she was there in the library!" Starlight argued, "and you're telling me neither you or your sister had anything to do with—"
"Detecting Fleur's presence within the library... was a simple matter of sensing her mana..." Castor explained, "neither my sister nor I... know what transpired within this tower... while we were away..."
"Oh... right," Starlight muttered, slightly embarrassed, "unicorns can do that..."
Twilight had remembered there were spells that would let a unicorn sense the mana of another pony. That was the reason she hadn't questioned how Castor knew Fleur was in the library. She knew, but of course, she said nothing aloud.
"In any case... I suggest you two return to your room..." Castor said, returning her focus to Twilight and Starlight, "due to extenuating circumstances... Mistress Aeon will not be back for some time... and in light of this new development... we are moving forward with your basic thaumatological studies... starting tomorrow..."
Both fillies had entirely different reactions—one whose knee-jerk reaction was of sudden unbridled glee and the other whose immediate reaction was shock, confusion, and the slightest bit of horror. The weariness of both, however, had completely, if temporarily, vanished at the news.
"Wait, seriously?! Just like that?" cried Starlight, "and when you say 'we', you don't mean—"
"We're finally gonna start studying magic?!" Twilight interjected happily, not caring one whit for who was teaching, so long as she was taught, "oh! What kind of lessons are we gonna start with? Wait, do we need textbooks? Are you gonna provide them or—wait, can we check them out from the library? Oh, maybe I can—"
"We will come to collect you... at seven o'clock sharp," Castor cut in, "get some rest... you will need it in the days to come..."
And with that, Castor's horn flare to life with bubbling black and violet light. And amidst the fillies' excited and indignant questions, her body shifted back into a black shapeless mass and she sank into the floor before quickly slipping away beneath the large black door that was the library's entrance.