The rest of the trip back to the main hall of the Fortress was a tense and uncomfortable affair for the foals. Starlight hadn't said a word since her initial outburst, and no one was willing to approach her about what had happened between her and Firebrand. Twilight was too caught up in her ruminations of everything she'd been through over the past few days to alleviate the tension. Firebrand, still feeling somewhat ashamed at his own behavior, was wise enough to keep his own mouth shut, though his own feelings on his personal situation hadn't fully changed, despite the new outlook on things provided by Starlight.
The two guards that escorted them through the maze of shifting halls had nothing to say on the matter and ignored the tension altogether. So things went until Night Runner finally announced that they'd left thestral territory and entered the main hall. If it hadn't been for the grandiose staircase leading up to the second and third floors at the other end of the hall and the few armored ponies and griffons patrolling the halls further up ahead, the fillies would've mistaken the large corridor for another one of the barren halls they'd just come from. One looked out one of the windows lining the halls revealed why there was so little activity.
The sun had long since set and the moon and stars were out on full display. The fillies had lost almost an entire day to their unintentional 'adventure' into the thestral's domain, and now it was most likely past curfew.
"How long were we down there?" Starlight muttered, staring out the window with a worried frown, "I'm pretty sure it was still morning when we got lost in that stupid maze."
"Hey, time flies when you're having fun, right?" Night Runner joked, causing Starlight to glare back at the thestral guard. Night Runner just shrugged and moved on, "I heard about the whole curfew thing. Bit weird if you ask me, but I wouldn't worry about it too much. I'm pretty sure something or someone's gonna—"
"Oi, you lot!"
Every eye in the group turned to see what Twilight and Starlight assumed was two of the Fortress guards quickly making their way towards them from across the hall. One was a griffon male, the other a pegasus stallion, and both were heavily in worn mail that'd been dulled to a murky grey color by age. Neither looked happy to see them all standing around an empty hall in the middle of the night, not when everyone aside from the Fortress guards were supposed to be tucked away in their dorms or barracks.
"Evening, boys!" Night Runner called out in a mock tone of joviality, "nice night out, eh?"
"Stow it, batpony," the griffon hissed with no small amount of distaste. The thestral mare narrowed her eyes at the griffon's tone, but he ignored her completely. Instead turned his attention to Iron Hide, "you wanna tell me what a couple of thestrals and..." he glanced down to see Twilight, Starlight, and Firebrand standing behind the two adults and his frown deepened as his gaze returned to Iron Hide, "...a bunch of foals are doing wandering around the Fortress after curfew?"
"Who knows?" Iron Hide answered, taking a challenging step forward and glaring up at the griffon, "why don't you ask that pony you all worship so much? Aeon, wasn't it? Maybe she can tell you."
Twilight had the sudden urge to point out that Aeon had also apparently been a prominent figure in thestral society as well, but that urge was buried under her current anxiety of what might happen next.
"Aeon ain't here right now, so I'm asking you," the griffon retorted, leaning down so that the two were nearly beak to muzzle, "look, it's been a long day, and I'd rather keep things civil, so why don't you make my job a little easier and tell me what you lot are up to, eh?"
"Iron Hide, just tell the birdbrain so we can move on," Night Runner sighed, "you know what'll happen if the Elders think we've been gone too long."
That... won't be necessary...
We can... take things from here...
A sudden chill settled over the bickering group and both Twilight and Starlight couldn't help but shiver involuntarily as an odd and wholly unpleasant tingle shot down their spines. Everyone else save for Firebrand drew their weapons, the two adult thestrals having lowered into a battle stance and brandishing hidden wing blades. The two disembodied voices echoed through the entire hall, the tone haunting and ethereal.
"W-What the hay was—"
"Starlight, look!"
Cut off by Twilight's sudden outburst, Starlight turned to the other filly to see her staring wide-eyed at something beneath both of them. The pale pink filly followed her gaze and barely choked back a scream as her own shadow began to twist, warp, and stretch outward towards the griffon and pony guards. It wasn't just Starlight's shadow either; both hers and Twilight's shadows elongated, pulling themselves further away from the pair of shocked and horrified fillies. The two guards for their part cried out in surprise and quickly shuffled away from the creeping shadows, their weapons at the ready for whatever came next.
Rather than attack, however, the shadows stopped just short of the two guards and slowly rose from the ground, their shapes morphing into something vaguely equine. Before long the pitch-black silhouettes of two ponies stood in front of the stunned guards. For a moment no one spoke, but the silence didn't last long, and to the surprise of Twilight and the others, it was the pegasus guard that spoke first, his eyes widening with recognition.
"Wait... a-aren't those..." he muttered shakily, dropping his weapon before nudging his fellow guard, "hey... Arne, wasn't there a rumor going around that Aeon caught two shades that escaped from Tartarus? I remember hearing something about her binding them to her service or something like that..."
The griffon gave his partner an incredulous look before returned his disbelieving gaze back to the shadowponies. He blinked once, then snorted and readjusted his stance before glaring at the two shadows.
"I... I don't buy it!" the griffon growled, "why would Aeon need shades under command? We've got perfectly capable Defenders to get done what needs to be done, right? I bet those damned batponies brought these things up with them from the depths!"
"E-Excuse me?!" Night Runner cried indignantly, "just where the buck do you get off you racist son of a—"
Oh, dear...
It seems... they don't recognize us...
I suppose... that's to be expected... given our appearance...
Shall we... shed our black guise... sister?
Must we, sister?
I think we must... lest the situation... escalate...
...Mm.
With the matter apparently decided and no small amount of confusion on the part of everyone else involved the two pony-shaped shadows suddenly blew away, scattering across the hall and vanishing into nothingness like dust on the wind. Standing in their place, bubbling black and violet aura fading from their horns, were two flesh and blood ponies—two identical unicorn mares to be exact. For a moment, Starlight thought she was looking at two other fillies, but upon closer inspection, the two were clearly mares, albeit on the shorter side.
Both wore black thinly plated, form-fitting barding beneath hooded cloaks not dissimilar to the one Aeon herself wore—although the jade brooch Aeon used to pin her cloak had been replaced by a simple circular clasp made of silver. Beneath their raised hoods, both mare's cloudy violet eyes and darker forest green coats contrasted heavily with snow-white manes that practically spilled down their face, their long silky locks nearly reaching the floor. The only real difference between the two mares, as far as Starlight and Twilight could tell, were the shape of their eyes; one mare had eyes that were wide and staring, giving the strange impression that she was constantly in awe of something. The other mare's eyes were half-lidded and sleepy.
Another trait they both shared, in particular, was the oddness of their gaze, their eyes both dull and piercing all at once. As if to complete the rather unsettling image, neither mare wore any kind of actual expression and when they finally spoke after revealing themselves, it was in a near-identical monotone.
"Castor..." said the sleepy-eyed mare.
"Pollux..." said the wide-eyed mare.
""Do you remember us now, Arne?"" they both asked simultaneously.
"Gemini," the griffon muttered, his angry and suspicious demeanor once more switching to disbelief, "so that's how it's going to be then, is it? You're to be the... escorts of this rabble?"
The mares slowly nodded once in response, never breaking eye contact with Arne. The griffon was silent for a brief moment, his narrowed eyes darting to the group of thestral. He clacked his beak in frustration but ultimately slammed his sword back into its scabbard before turning away from them all.
"Very well then," he finally replied, grimacing in displeasure but giving the group of foals and thestral guards a curt nod over his shoulder all the same, "...as you were."
"W-Wait, what?" the bemused pegasus guard asked, whipping around to face his retreating partner, "Arne, what's going on? Who are these two?"
"I'll tell you later, rookie," Arne snapped back, "now pick up your weapon and get back to your post! We're done here."
The stallion, apparently a rookie guard, jumped at the command and snapped his weapon back up. He turned to give the twins and the rest of the group one last bewildered look before hurrying after the senior guard. The moment they were out of earshot, Starlight spoke, her voice quiet but carrying a weight the everybody else could feel nevertheless.
"Can somepony please explain what the buck is going on?"
It was a fair question, and one that filled the minds of each thestral present. Twilight, for her part, stared at the two identical mares as they finally turned their attention to the remaining group. They looked nothing like them, but the mere fact that they were twins triggered something in the back of her mind, and her stomach twisted in painful knots at the memory beginning to rise to the surface. With an effort far beyond what she thought herself capable of she pushed the memory back down, remembering the rousing speech she herself had given Starlight that very morning before they both had stumbled into their little 'misadventure'.
I have to move on...
With that thought, she moved her focus to other, more important things. Things like the fact that those two mares had apparently been using Dark Magic to hide within their shadows.
"How long have you been following us?" Twilight asked the mares, her question completely overriding Starlight's as everyone looked in her direction, "you were using Dark Magic to hide yourselves, right? I saw it when the shadows went away."
"Y'know... I bet they were sent by Aeon," Starlight guessed, her eyes narrowing with immense suspicion, "knowing her, she probably had them tailing us since before we even got lost."
"Wait, seriously?!" Night Runner exclaimed, looking from the fillies to the twins. Something seemed to click in her mind and she frowned at the two warily, "...is that true?"
"Spies," Iron Hide grunted with a disgusted sneer, "using fillies to gather information. Knew that arrogant nag couldn't be trusted."
At the accusations filed against them, the twins glanced at each other, their mostly blank expressions unchanged.
"It appears they've... made some troubling assumptions, sister..." droned the sleepy-eyed Castor.
"It can't be helped, sister... they are not... entirely wrong..." came the equally languid reply of the wide-eyed Pollux.
There was another brief pause while the two glanced at each other. This time there seemed to be some kind of silent conversation taking place between the two and this was confirmed when Pollux nodded and stepped forth to address the others.
"We were, the two of us... ordered by our Mistress... to watch over the fillies while she is away... this much is true..." the mare explained before turning to the two thestral guards, "we have no interest... in your sanctuary... our Mistress knows all she needs to know... about the city of Nightshade..."
As the fillies parsed these words and began to realize what they implied, Pollux wrapped her horn in a bright yellow glow and levitated a rolled-up scroll from beneath her cloak.
"If you still require convincing... then show this to your Elder... the one called Dusk..." Pollux continued, floating the scroll over to Iron Hide who, rather than take it right away, eyed the piece of parchment with a wary scowl, "I'm certain... this will clarify things... feel free to read it if you wish... though I doubt you could make sense of what is written..."
In response, Iron Hide snorted and snatched the scroll out of the air before pulling it open and scanning the parchment. Curious, Night Runner moved closer to Iron Hide so that she could read over his shoulder. As the two read whatever was written within the letter, Twilight and Starlight took the opportunity to speak, both fillies already coming to the same realization by now.
"So you've been with us this whole time?" Twilight asked taking a step forward, "since before we got lost? Since before we were trapped in that maze? Since before we got attacked by a manticore?"
Pollux nodded.
"You two were there, supposedly 'watching over us' on Aeons orders?" Starlight supplemented, getting another nod from Pollux, "okay... so tell me, what does 'watching over us' mean to you two exactly? Because I was under the impression that 'watching over us' meant... I don't know, maybe jumping in to help us before we get mauled and eaten by a massive rampaging beast!"
Neither mare said anything in response, nor did they show any sign of shame or guilt.
"I... if I hadn't... If I hadn't killed that manticore..." Twilight said in a shaky near whisper, "if my magic hadn't gone out of control like that, Starlight and I would've died... if you were there, why didn't you do anything? If you'd helped us back then, I wouldn't have had to—"
"You did... what was necessary... to survive..." Castor cut in, moving to stand next to her sister, "exactly... as our Mistress intended..."
"I... what?" Twilight asked, a bewildered frown crossing her face.
"This is not a place... meant for the weak and sheltered..." Pollux explained, "you will find... very few creatures willing to hold your hoof... our Mistress understands this... and wanted you two to understand as well..."
"The day was yours to do with as you wished... we were merely meant to observe..." Castor continued, "only in the most dire circumstance... were we to intervene... as our Mistress ordered..."
"And that... all of that back there didn't count as 'dire circumstance'?!" Starlight shouted in indignation as she gestured in the general direction they'd all come from, "we were nearly eaten! We were thrown in jail... again! Who knows what those Elders would've done to us if Nightmare Moon hadn't showed up! Oh yeah, by the way, Nightmare Moon showed up! The Mare in the Moon herself!"
"We are aware... we witnessed as much for ourselves..." Castor replied dully, "and no... none of that qualifies... as dire circumstance..."
Her gaze shifted briefly to Firebrand, who'd been quietly observing the entire situation with no small amount of shock and confusion. Seeing he had the mare's attention, he jumped slightly and shrank further back behind the two fillies. Castor only blinked once at that and returned her attention to Twilight and Starlight.
"You should also be aware... that had we interfered then... your punishment would have been... far more severe..." she pointed out, "justice meted out so swiftly... that Nightmare Moon would've had no chance to intervene on your behalf..."
"What? Why?" Starlight asked incredulously, "what would've happened?"
"The Elders—well, most of them—were willing to be a bit more lenient because they understood that you were foals who got caught up in something you didn't understand," Night Runner explained, having read the letter with little comprehension of what it meant, "if the two of you had been adults or were found guilty of colluding with adults to sabotage the trial—specifically with intent to kill Tenebrae... well..."
"Let's just say that Elder Sanguine Oak probably would've had his way," Iron Hide finished, rolling the parchment back up and stuffing it in his armor, "and if he'd had his way, the whole lot of you might've actually had your horns removed."
"Y-You wouldn't..." Starlight stammered, her pale face moving from Iron Hide to the twins, "you wouldn't let that happen, right? That would count as dire circumstances wouldn't it?"
"It would..." Castor replied after a moment.
"We would, at the very least... not allow ourselves to fall victim to such a fate..." Pollux continued, "we would fight to escape... and we would do so with ease... but in doing so..."
"A pact... between our Mistress and the thestral race... would be broken..." Castor finished, "it would be... very inconvenient for Mistress Aeon... if that were to happen... but she was willing to take that risk... because she believed it would not come to that... and she was right..."
"You did well... Twilight Sparkle..." Pollux added with a nod towards the filly in question, though her expression still didn't change in the slightest despite the praise, "Mistress Aeon will most likely be pleased... to hear about this development... when she returns..."
"Wait... so hang on a minute," Night Runner chimed in with a frown, "you may not have been caught, but we're still here, and we just heard... all of that. What's to stop us from just—"
"Forget it, Night Runner," Iron Hide sighed, "unlike you, I more or less got the gist of the situation from the letter. If I'm reading this right, then the foals are basically off the hook," he turned to glare at the twins, "...and so are they," that said, he grunted in frustration, spat to the side, and turned to leave, nearly bowling Firebrand over as he practically stomped away, "our work is done here."
Night Runner watched him go for a moment, before shaking her head and turning back to the twins. She wanted to say something else and opened her mouth to do so, but then realized there wasn't really much else to say. They'd brought the foals to the surface just as instructed, and everyone was in the clear, despite the violation of this pact, whatever it might've been. She thought about asking who the mares actually were, but not only did it not matter because odds are she wasn't going to see them again, but she also got the distinct feeling the answer was above her pay grade. And so, deciding it wasn't worth it, she simply shrugged her shoulders and turned to follow after Iron Hide.
"Welp, I'm not sure what this is all about, but I guess I'm supposed to leave the rest to you two," she said, a hint of bemusement still lingering in her tone. She stopped next to Firebrand and, on a whim, leaned down and whispered with an impish grin, "hey, kid... tell me about the surface when you get back. I wanna know if being a Defender is worth the trouble."
With that, she trotted off with a wave of the hoof and one last goodbye to the group. That left one confused thestral colt, a pair of eerie chaperones, and two very troubled fillies with a multitude of questions standing in the nearly empty moonlit corridor.