"It's dark," the guard spoke in a hushed voice.

"It is always dark down here. The only light you may have is what we will provide. Those lights may only be used at your post, this path must stay dark at all times." The second guard also spoke with a subdued voice. He was more decorated, his golden armor of a slightly older design than his companion's dark blues and purples. They walked through the dank tunnel, the dark stifling and oppressive all around them. "These are the basic rules to your new assignment: No unicorns are permitted past your post. Magical items are absolutely forbidden. Only those with a writ of consent with the seal of the Princesses themselves are permitted within your post, including myself. Pegasi must be fitted with a suppression harness if they have the necessary writ. These and plenty more rules, not to mention finer print, will be in the post logbook's inside cover. When you reach your post you will be fitted with a specialty weapon that you must wear at all times, including off-hours. You may only train with this weapon against the dummies provided. Its use against your fellow guards is punishable by imprisonment by decree of the Princesses. Training with these blades will be required, and a standard amount of hours will be logged. Do you have any questions?"

The briefing had been smooth, well practiced, and articulate. Despite this the recruit not been listening closely; his attention was drawn away by the inky darkness in the tunnel. There was something about the blackness that sent shivers down his spine. He willed his mind to focus on his superior officer and the briefing he had just been given.

"One question, sir," the night pony asked. "Why was I picked for this detail?"

"The answer to that is simple: You are top of your cadet class in combat and efficiency scores; you have no mate, no dependents, and no responsibilities outside yourself; lastly you are not an only child so if you don't survive your family name is not in any danger."

The recruit's ears dropped so suddenly that they slapped against the sides of his helmet.

The officer noted the recruit's reaction, and added with a calmer tone, "Carelessness in this position has cost lives, recruit. I hope you will be cautious and follow the appropriate instructions."

"Yes sir, of course sir," he said solemnly. "I wouldn't imagine doing anything else. Especially if it means death." The night guard turned his head to look into the darkness as they walked, his expression hardening. "I have a lot of reasons to go home, even after-" he paused for a moment as he considered his words carefully, "my qualifications."

This drew a smirk at the edge of the officer's mouth. "Good. I have found a healthy desire to continue breathing is often the greatest motivation for excellence."

"Are the prisoners down here that dangerous?" It was unnerving even to ask, as visions of bizarre and deadly creatures flitted through his mind.

"Prisoners? Prisoner, no plural," the officer spoke with a grumble. "There is only one occupant in this forsaken place. The entire path we have walked is just the entrance to his cell. Your post is the guard's quarters and gateway leading to that cell."

"Buh," the recruit fumbled his words as he gaped dumbly. "An entire detail, a full six month duty shift per rotation, all for one single prisoner?"

"That is correct. And, if you are one of the luckiest, you will never have to meet the thing you are guarding face to face. At least hope you won't have to meet him for any extended period of time," the officer said. "It will be healthier."

The pair reached a grand door that looked to be constructed of solid iron, golden markings and rivets glowing on its surface. The glow had emerged from the gloom and murk before them rather suddenly, as if the entire tunnel was filled with a fog so black it swallowed the light.

"Commander Stout Shield to escort Night Guard Ion Cloud to his new post!"

There was a bass clank so deep it sounded as if a mountain of metal had been shifted behind the door. With a grinding rumble, the door slid to the side just far enough for a single pony to walk through.

"This is as far as I go, recruit. I do not have the necessary writ to pass beyond this point," he said, nodding towards the door. "You will receive a further briefing, your weapon, as well as final instructions within. Good luck. I hope to see you again in the service of her Majesties above." Stout Shield saluted, did a crisp about-face, and within a few seconds vanished into the gloom of the abyssal tunnel.

Although the space beyond the door was gloomy, the torches lining the walls and pedestals provided better light than had been in the tunnel. A quick glance showed them not to be crystal flame torches, but gas nozzles. Each one had a funnel above it that led to a tube system creeping into the ceiling. The same metal that the door was comprised of coated the ceiling and the walls. Those same glowing gold marks and rivets were there too. Ion Cloud's gaze ventured up to a second floor carved into the side of one of the tall walls. He noted each of the sides of the box-shaped expanses had such a carving into it. All the second floor areas were lit with the gas torches to expose meager living quarters, eating areas, and armories. No amount of space was wasted, a textbook definition of basic post barracks. The assignment brief had not been misleading in the slightest. It only took a few moments for other guards in the area to assemble, all looking at their newest comrade.

Ion Cloud was expecting leers and angry glances in response to a new face arriving, but none came. Only calm glances, weary eyes, and even a few looks of relief came his way. The other interesting aspect was the mix of night and day ponies, and none of which sported a Unicorn's horn.

"Ion Cloud, I am Captain Red Pine," a decorated officer spoke as she approached. "I see you are a Night Pegasus; be sure that you are fitted with a suppression collar within the hour. The area you are in is the Oculus, the primary area for living and training. Your bunk is up there in the night shift section, grab any one that is empty. Your belongings have been delivered and are waiting on the mezzanine opposite the living quarters. You will be issued a logbook and a duty roster. I don't need to describe my expectations. Do your best and we can all go home. Meet your shift partners and get to know them. Refer any questions to your shift leader, Midnight Harvest. You have two hours to acclimate before your training shift begins." Yet another obviously practiced speech. The whole of it had Ion Cloud a little blown away. He had never been a part of any military assignment that functioned this smoothly.

As the Captain moved away, a Night Pony walked up to take her place. "You'll catch on. Come this way," he said as he headed towards the living areas.

Following the Night Pegasus that had spoken to him, Ion Cloud did as he was told.

"Easy to get caught up around here. Don't worry about the little details. Let's get you in a suppression collar, armed, and learning the ropes. I'm Midnight Harvest. We tend to pair night ponies with night ponies and day ponies with day ponies, so you'll likely be with me on shift since the guy you are replacing was one of us. Sometimes we get mixed, but it doesn't usually happen. So, got any questions?"

"What in the name of Celestia is being held prisoner in this place?" Ion Cloud sputtered.

"Hah, that's everypony's first question. Most then want to know where the food is served. Suppression collar first, though."

Ion Cloud frowned at the fact that despite being given leave to ask, his question remained unanswered. It took a few minutes, but the rune-covered metal neck coffin they called a collar was finally fitted to his neck and sealed shut. Immediately, the room seemed a little brighter.

"And before you ask, yes we are suppressing your natural magic. Also, no this is not so you will die when you try to walk on the clouds this nasty place very obviously does not have. Earth ponies have very internalized natural magic, so they're immune. Unicorns have too much expressive magical ability, so even with a suppression collar they are still susceptible. Pegasi of either type fit right in the spot between latent and applied magical powers so that the suppression collar works." Midnight Harvest snapped the last clasp and hammered the bolt closed to complete the fitting.

"What is this supposed to keep me from doing?" Ion Cloud asked as he fidgeted at the thick metal around his neck. "I mean, it isn't like I would be flying a lot down here, and I can still glide without magic. No clouds to walk on as you said, or weather to affect."

"It isn't to keep you from using magic-that's just a side effect. It's to keep him out. Our, ah-guest." The two guards walked towards the massive door opposite the entrance. "He can use your magic somehow-get in your head. If you had gone much longer without this, you would have started hearing voices. Once you hear the voices, we have to get you out of here or-well-bad things happen."

They reached the door, and Ion Cloud saw the immense and mind-numbing mechanics that made the monstrous things move. He'd passed through one already, so he knew how thick they were. This was the monstrosity that worked both doors, and it made sense why such huge machines were needed. He could have stood nose to nose with his new partner and the door would have been thicker than the two of them end to end. A single link of the chain looked like it could easily weigh half a ton.

"Only one way in, one way out," Midnight Harvest noted. "Both doors can only be opened from right here."

"So, that's his cell? Whoever we're guarding?"

"Nope, that's the door to where his cell is. Here, that's part of the in-processing anyway." He looked up to the door controllers and hollered to them. "Two guards to the cell-block!" They began to work quickly, the same deep and fearsome clangs and thunks of the door arising as the chains began to move. With a slow grinding, the door slid away from the rock wall and opened. There was no eerie pitch-black fog as had been in the tunnel. Instead, a subtle green light emanated from the opening. Midnight Harvest nodded towards it saying, "Hang on to your helmet."

The two guards moved through the opening and the door immediately closed behind them with a thunderous boom. Ion Cloud clenched his teeth as his eyes adjusted. "Buh," he muttered once again. "How can-how is this beneath the castle? It's huge. How can something like this exist and no one in Canterlot even be aware?"

"We have a pretty tight lid on this place, and Princess Celestia makes sure it stays that way."

"But this," Ion Cloud trailed off. The room was enormous. He couldn't even see the ceiling, only a number of pillars rising up into the void. There were eight of them, all aligned around a single point in the immense room. A house could be built within it and there would be space left over. At the center, amidst magic runes, glowing lights, markings in the stone and pillars, and chains crisscrossing and connecting like a twisted web was a single barred cell. The sight of it chilled Ion Cloud's heart, his blood turning to ice. They approached, but came no closer to the cell than the web of spiked chains. The huge circular spell rune underneath the cell gave off the bright green light exposing the single occupant. "What is-is that the prisoner? I don't even recognize it."

"No creature like it has ever been found or seen as far as I know. We don't even know why it's down here, or even how long it's been here. The Princesses are the only ones who know and they only give orders to us, not explanations." Midnight nodded towards the prisoner as he continued, "Thank Celestia it's sleeping. It does that a lot. Pray you never have to listen to this thing talk for long."

"It can talk?"

"Yeah, it can. I still have nightmares from when it decided to have me for a conversation partner."

"What is it? Do we at least know that?"

"We have a book with a single record of it by a researcher named Virtuous Sight. She claimed that it's called a 'Sapien.' She studied it pretty extensively from a safe distance after the madness effect was discovered. Though, I think that is the reason she-uh-died. Starswirl the Bearded tried picking up her research some time later, but the effect this thing has on magic-well, they all eventually just gave up."

"Wait, Starswirl? My brother told me about that unicorn. He lived back when," Ion Cloud paused a moment. "I thought you said there hasn't been one found before this one."

"That's right. This is the only one. Been down here a long, long time. More than a thousand years as far as anyone is aware. Like I said, only the Princesses know. Far as we're concerned, it can stay in here." The conversation was interrupted by a dull banging, like a bell, though it gave off barely any echo. "Uh, okay. That's the recall, guess we're cutting the acclimation short. So much for explaining the cell, but you can read up in your logbook. That sound you just heard, that usually means something big and we all need to report. So, come on. Guess it's into the deep end for you on your first day."

The immense door was already opening when the guards reached it, and soon they were bounding through back into the Oculus. Ponies fervently busied themselves cleaning, assembling, sorting, and organizing as Captain Red Pine walked to and fro barking orders above the din. "I want weapons presented, armor polished, and records prepared for review! We assemble for the formation in one hour, inspection to follow immediately! We will be ready! This detail doesn't mean laxing just because we are underground! We are still soldiers of the Royal Guard, and we will look like soldiers of the Royal Guard!"

"What is going on?" Ion Cloud asked as quietly as he could.

Midnight Harvest shook his head as he answered, "Haven't seen this much bustle since Royal Commander Shining Armor came through. Must be a hot shot."

"We were only gone a few minutes though."

"That's all it takes sometimes. Come on, let's get you a weapon and get to buffing. Captain Pine is a bit of a perfectionist, and she really means what she says. We have to be prepped for top brass when she gets like this."

"Are there often inspections?"

"Nope, this is unusual. Something big is gonna happen."

"Big? How big?"

Midnight Harvest chuckled as he opened a metal case and pulled a strange two-pronged blade out, identical to the one at his own side, and fitted it to Ion Cloud's pauldron. It locked with a snap. "Well, I've only heard about it happening for a while-but when things get this crazy it usually means royalty. Congratulations, first days are always the most interesting."

"Royal-buh," came the signalling sound of Ion Cloud being left dumbstruck.

Midnight Harvest rapped the side of his partner's helmet with his hoof to shake him out of it. "Yeah, as in Princesses, maybe. Sometimes a Royal Commander, sometimes a General. Doesn't matter; we have to be ready."

Amidst the chaos, Ion Cloud met his comrades haphazardly between scrubbing the duty tables and rebuffing each floor panel individually after a failed first inspection. Along with Midnight Harvest, Quasar and Hunter Ellipsis were the others assigned to his immediate group. It had been some time since he'd been in a group composed entirely of Night Ponies, and he drew comfort from what they shared.

Clenching his teeth, Ion Cloud scrubbed a stubborn scuff on the metal floor. Blowing on it for good measure, he stood and grinned at his handiwork. Dad had always made him do the hard cleaning, and now that attention to detail was being put to good use. The bell sounded again, sending every guard pony in the entire facility hurrying to the central point. They lined up in sharp formation, snapping to attention with heads held high. Taking his spot with the other Night Ponies, Ion Cloud made sure his stubborn left pauldron was sitting straight before freezing at attention himself.

The grinding and grumbling of the huge gears and mechanisms announced that the doorway was opening. It rumbled to the side revealing brilliant white light instead of the usual thick black fog of the tunnel. It kept going, opening farther than before to show the source of the brilliant light.

"Company!" Captain Red Pine's voice rose over the sound of the great door. "Present, arms!" The smooth, simultaneous movement of blades rising in honor greeted Princess Celestia as she halted just inside the threshold. No eye drifted her way, the formation remaining unmoved. The Night Ponies especially were not tempted to look as they had to squint, their eyes not made to handle the level of brightness that was beaming from the Princess.

"We were not expecting you, your highness!" Red Pine was still bellowing despite the door no longer filling the expanse with the sounds of its workings. She coughed and adjusted the volume of her voice. "To what occasion do we own this unexpected honor?" The captain's eyes drifted from the Princess to a half dozen of her personal guard taking station just within the door. Her eyes snapped back to Celestia as the Princess addressed her.

"I wish to speak with the prisoner," she said in a dulcet tone. She looked kindly at the steely visage of the captain before nodding her head towards the formations before her. "This seems unnecessary, we ask enough of you all as it is."

"Hardly unnecessary, your majesty! We have prepared the post for inspection if you wish." With a crisp turn Red Pine took her place at the front of the formation and snapped to attention.

"Company creed is 'duty and honor before all,'" the tiniest of whispers filtered to Ion Cloud's ear. He moved his eye just enough to see Midnight Harvest looking at him and then give the slightest of nods.

"Order," the captain's loud voice echoed through the Oculus. "Arms!" With the same fluid motion, the guards lowered their weapons as one.

"DUTY AND HONOR BEFORE ALL!" They thundered with a single voice. The Princess smiled warmly, obviously enjoying watching her soldiers and the ceremony, icons of a time immemorial but still true examples of discipline and order.

"Captain, if you would be so kind," Celestia's voice sounded as bright as the radiance her magic gave off. It was the one piece of hope inside the dreary Oculus at that moment.

The gears of the entrance door began to turn, the mountain of metal beginning its slow return to close. Opposite them, the door to the cell-block began to wind and rumble as its machinery ground to life. "Valor, have your guards await me here. I will address the prisoner alone."

"Your majesty, you know I do not approve of this," the leader of her personal guard said unemotionally. Every guard and soldier within stiffened at the thought of the Princess proceeding alone.

Ion Cloud too felt a shiver run up his spine at the thought, especially after what Midnight had been telling him. Why was the Princess going in alone? What could she want with a prisoner buried so deep that only the guards knew it existed? None of this felt right in his chest, but he kept himself rigid. It was not his place to question.

"I do not require your approval, Commander. Only your obedience." No matter how sweet her voice, Princess Celestia's words wilted every ear that heard her rebuke. "This is not a matter I will debate."

"Of course, my lady. By your will." The Commander had been unemotional before, but not now. Despite his show of fealty, there was anger in that response.

Ion Cloud could tell; he felt the exact same way. He had seen what was contained on the other side of that door. He knew a little about magic, enough to know one thing: whatever was contained in that dark and forbidding room was a beast. The very presence of it felt as if it would soil the pure light of their ruler. Whatever sort of creature this "Sapien" monstrosity was; it was evil. Ion Cloud could feel it in his heart, and he had a very strong sense that feeling was shared by any who had any kind of experience with it, no matter how short.

As Celestia strode between the two lines of guards, they no longer kept to their strict, unmoving position. Their eyes followed the Princess as she strode towards the opening doorway. All but the Night Ponies, who clenched their eyes as she passed, watched with trepidation.

They knew that the Princess had visited with the prisoner before, but what she could possibly wish to discuss with the creature was an enigma. Although they did not question this not a single one of them wished to simply sit by and allow her to go alone into that hellish room filled with dark magic and fearsome chains.

When the door had opened and the green light poured through, Princess Celestia pressed on. The light of her horn almost seemed to battle the green glow of the magic within, pushing it back into the dark depths. A few more sharp clacks of her metal-clad hooves and the Princess passed beyond the second enormous door. As soon as she did, the white light of her horn was swallowed up from the guard's sight, and the green poured through once again. The gears roared to life, and the door began to close.

"Company-fall out." Captain Red Pine no longer bellowed her orders, her voice swept up in the din of the machinery. The guards of the Oculus all relaxed, but instead of dispersing they gathered and watched as the great door finally closed with a thundering boom. Every pair of eyes stared as they waited for something to happen.

Nothing did.

"First days, always eventful," Midnight Harvest whispered to his comrade.

Ion Cloud did not respond, only stared at the door with a feeling of dread in his heart.