Cadance blinked at the spines all around her. Canterlot Castle was filled with many libraries, book-nooks, and archives, but Luna's various studies and personal libraries were not like most of the others. Auntie Celestia had row and rows of books on nothing but politics and law. Every offense possible could likely be found within the covers of those dull, rambling volumes her aunt kept on the higher shelves, where not Faithful Students could reach them.

But even the spines of Luna's books were different. Everything about them was, really. First off, there were far more of them. Shelves were overcrowded with everything, and there was a drastically less sunny, social vibe than in Auntie's libraries, where books felt more like furniture than the centerpiece of everything. Such a thought was clearly disregarded by Luna, who had model airships, buffalo dreamcatchers, classical paintings, and framed maps with ornate writing so old Cadance couldn't even read the names when squinting decorating non-book surfaces.

Cadance had stopped questioning how it was Luna manged to obtain so many unusual volumes in such a short span of time since her return, accepting there were many mysteries to Luna she would never be able to make heads or tails of. She was, however, a bit curious about the age of some of the thick books. They looked positively ancient, and aside from archive materials within their respective locations, Auntie Celestia had only kept ancient law books, since so many of the laws from the dawn of Equestria as a nation were still in place.

Titles jumped out at her, boasting a vast assortment of things from magic theory, botany, warcraft, mental health, spells, crime, poetry, various bestiaries both ancient and modern, and quite a few books on various parts of opera. Extra curious, Cadance had discovered when she carefully withdrew the volumes from their cozy nooks, she would be greeted by the carefully painted covers depicting elegant costumes and opera houses, including Canterlot's own. She made a mental note to ask Luna more about them, hoping that they could look over them together, as one musical enthusiast to another, and that Luna would have a story to spin.

What really caught her eye, however, was something towards what was clearly a fiction section that housed the epics, tragedies, and thick books in nearly every genre except romance. It was an older piece, but not remarkably so, and likely only so much older than Cadance's own parents. Some edges of the faux leather cover had been worn, but Cadance didn't doubt that Luna had laid proper preservation enchantments on the book when it fell into her hooves.

The letters, though, were still quite clear, giving the title as Equine Races and Their Legend, Vol. 3.

It absolutely did not strike Cadance as something that should be in the fiction section, and her muzzle crinkled in confusion. She had encountered various other volumes in the series in the non-fiction area of this particular library, and while Luna was no Twilight Sparkle, she sorted her books well. Each volume in the series gave a history of traditions, other cultural quirks, curious health information, and overviews of the various equine races, real or considered less so, and an examination of various myths and folklore about and within the pony race, creating an odd sort of anthology.

Volumes on pegasus ponies, earth ponies, and unicorns were easy to find, and the ones on zebra, donkeys, breezies, sirens, and sea ponies were as well. However, Luna somehow wasn't able to get her hooves on a volume about the mysterious Alicorns - if one even existed - and because of information available at the time, there were no volumes about crystal ponies or ponies like Cadance herself, because there were no 'lesser alicorns' that came before her.

Oddly enough, changelings were erroneously considered 'equine' by the author, and they had clearly botched their description of changeling hive structure, as well. Though, Cadance didn't blame them. Few wanted to get close to a changeling hive, if they could find one at all.

Admittedly, she had spotted a few other volumes dotting the fiction section in public libraries, since the series was not entirely unfamiliar to Cadance. But, it made sense that somepony would see a book about flutterponies or kelpies and know that they belong with fiction.

But this one? The small bat wing that Cadance spied on the spine was peculiar, because it likely only meant one thing. She lit her horn and her pale blue aura made contact with the book, carefully pulling it from its place and turning it over so the cover was in plain sight.

The painted image of a bat pony greeted her, shadowy and flying through a night time forest.

Cadance blinked again, her muzzle getting extra crinkly with thought.

"Luna!" she called, swiveling her ears back to catch the sound behind her.

"Yes? What is it, Cady?" came Luna's response, and the sound of hoofsteps approaching her.

Soon, Luna stood at her side, eyes calm but ever-curious as the young goddess looked at her. "Is there something wrong with this book?"

For a moment, a small frown crossed Luna's muzzle. It was one of her more usual expressions to have such a slight, neutral frown. Most ponies didn't recognize that it was a sign Luna was thinking about something deeply, or that plans were on her mind, and she was unjustly dismissed as sour sometimes - which she wasn't - or aloof - which she certainly could be, but that wasn't a problem for Cadance. Even Auntie Celestia made this mistake so very, very often.

Cadance knew better than to call Luna detached, though. No detail escaped this mare, even when you thought she wasn't watching things.

"Why's this in the fiction section?" Cadance asked, levitating the book closer to Luna, who simply cast her gaze at it.

"Why shouldn't it be placed so?" Luna asked levelly in reply, eyes now watching Cadance coolly. There was a slight gleam to them, one Cadance could only figure meant that Luna probably already knew the answer.

"Well, uh, don't you see?" Cadance's magic waggled the book back and forth.

"Indeed, that is a book."

Sighing, Cadance tapped the art upon it lightly with a hoof. "Look at the cover, yo."

Luna did, or rather, she already was. "I do suppose that the artist must not have had the best technique for when it came to painting pine needles. Do you see how they are closer to smooth strokes with no fine details? It begs the question of if they got out often, or if they simply were not taught as well as one could hope."

"...There's a bat pony on the cover."

"There certainly is," Luna said, an impish sparkle in her eyes and a tiny smirk on her muzzle.

"Yes!" Cadance exclaimed, tapping the book again. "There's a bat pony! And it's in the fiction section!"

Luna nodded. "As it should be."

Thrice, Cadance blinked in an expression of proper mild confusion. "Whaddya mean?"

"My dear friend, surely you realize that bat ponies aren't real?"

"Uh..." Cadance swallowed, tucking the book under one of her wings as a forehoof moved to play with her curls. "What?"

"They are not real," Luna repeated.

"But that can't be true! Bat ponies are totally real, just like you, or me, or bad mane-cuts."

Luna cocked her head to side, blowing her bangs out of her eyes when they fell into them before she calmly trained her eyes on Cadance once again. "Do you think them some race of their own?"

"Err, yes."

"And I suppose that you think they live off in some dark place, likely underground, as diamond dogs and changelings do?"

"Well... I'm pretty sure that they live in dark forests and stuff too," Cadance mumbled, kicking at the floor with a forehoof.

"Ah, I see. When you sleep, do you think that I have my own guard you cannot see, composed of these creatures?"

"Um. Sometimes?" Cadance's ear flicked hesitantly.

Luna tilted her head so far to the side that her mane rippled and swished more than normal and she ended up looking more like an owl than a pony. "But why do you believe such things?"

Was this a rhetorical question? Philosophical? Cadance quickly scrambled through her thoughts in a hurry to find an answer, but instead just wondered why it was only Luna who enjoyed challenging the things she believed in. If she ever met another pony as weird as this, she knew she'd just lose her mind.

"I've seen some bat pony guards around the castle at night... and they look different, their armor is different. There's countless legends about them-"

Luna arched an eyebrow. "Countless legends also said that I was not real. Before my return 'Nightmare Moon' was 'just an old pony's tale' and 'Luna' even more so. There is much truth to be found in many legends, but there are always some that are pure fancy. Bat ponies are one such thing."

"Wait, but how, Luna? How can bat ponies not be real if I've seen them with my own two eyes?"

When Luna beckoned Cadance to sit down on the floor, she did so, surprised at there being no cushions or chairs. Auntie Celestia was not a mare who sat on floors, but Luna was, and she was a mare who was apparently going to try to disapprove bat ponies too.

From under Cadance's wing, Luna's magic pried her book, and her own dark forehoof came to rest on the picture. "This is a legend sprung from a few incidents of certain spells gone wrong, and little else."

Cadance's crinkly muzzle returned. "Like when Twilight wrote to be about how she accidentally turned one of her friends into a bat?"

"Exactly!" Luna said with a bright smile. "Though, most spells that resulted in 'bat ponies' are not quite of that calibre. Legends made them appear much less grotesque then they truly were. Most of their supposed habits were either just borrowed from true bats, or from illnesses a pony gets when they attempt truly omnivorous, and even cannibalistic crimes."

Luna may be able to discuss many macabre things with ease, but Cadance shivered at the mention of unnatural meat-eating and cannibalism thrown about so casually. The library felt just a bit colder, as well, but Luna continued.

"Myths about a silly kingdom for what started as little more than transformation and meat-mad ponies were the only explanation simple-minded everyponies from ages past had, and clearly-" Luna rolled her eyes, "-it was far more of a taboo to exist in any solitude. A race of monsters had great appeal, and the foals who would be raised on such tales as entertainment would then tell it to their own foals as though it were fact. Still, many more habits of your 'bat ponies' are just copied from the tales of vampires."

"Wait!" Cadance all but shrieked. "Vampires are real, aren't they?!"

Luna blinked at the outburst, but offered no other physical reaction. "No, they are not."

"What? B-But? How?" Cadance sputtered.

"Cadance," Luna began, giving the other mare a flat stare, "How much of your concept of 'bat ponies' and 'vampires' comes from more shallow young adult novels that have even less of a proper grasp on the legends than usual?"

"Uhh... pass?" Cadance squeaked, unable to meet Luna's gaze.

Luna crossed her forelegs across her chest and set the bat pony book down in front of her, mane rippling with a visible increase in attitude. "I suppose you do not realize that 'vampires' are little more than a weak and tasteless corner of folklore built entirely on the danger of encountering a succubus and one of her drones, and the violations and violence they will bring to ponies?"

Cadance's tail swished across the floor in confusion. "Succubus?" she echoed.

"Yes," Luna said, "a succubus is a changeling queen who, while appearing no different from a regular one, is corrupted, and because the queen is corrupted, the hive is as well. Your Queen Chrysalis was such a being, and I'm sure if you poked you muzzle into different, less fictitious contents of my libraries, you would learn that before treaties were made with many hives in my absence, attacks on ponies in the time shortly before and after Discord saw many attacks on ponies and changelings by one another."

Rubbing at her coat awkwardly, Cadance just offered a distracted 'oh' in reply.

Luna noted this and nudged forward the book with a push from one of her forelegs. "Do you still wish to know about the guards that you see around the castle?"

Cadance nodded.

"Good," Luna said, giving Cadance a small smile, "The guards are the same guards you see in the day, you silly mare! I have none of my own! It is called the Royal Guard, and not Celestia's, but with my return, there is a now a balance that I can bring via many of the magics I have that Tia does not. I have nocturnal senses, something nopony and no other Alicorn in the present has. With my magic, I can offer the hardworking stallions their own sliver of abilities greatly lesser to but like my own. This changes their appearance, and the fact that their armor hides their marks is why you would not recognize them."

"Oh," Cadance mumbled, "wow! So, they're just a day shift and a night shift, but the same ponies?"

"That would be correct."

"Uh, so what about the armor?"

"Ah!" Luna beamed, another playful smile shooting across her face. "That would be my work. I sponsored many a crafty spell-smith before... well, you can guess. This was back when the art was scorned and not recognized for what it was. Ponies were content to work metal first, and then magic, as the armor for the 'day shift' and most conventional armors have been made. Though spell-smiths are great and influential now, those that worked magic in the metal as it was still shaped to create the most fabulous things were not respected, partly for how unusual their works were. 'Night shift' armor is old, but in a most fantastic shape, and made in the ways of old to have greater magic that a pony would need when working in the dark. Some of the uniforms still in circulation I even made myself, in my amatuer days."

"That's..." Cadance winced a little, "a far more underwhelming answer than what everypony else thinks about bat ponies, vampires, and bat pony vampires... but still really cool, yo!"

Laughing merrily, something she hardly did around anypony, Luna thrust one forehoof forward, and nearly mashed it into Cadance's muzzle. Yelping and shocked from the boop of godly strength, curls flew and Cadance fell backward, her wings springing out in spastic surprise.

The last thing she saw before she fell to the floor completely was Luna triumphantly sticking her tongue out and the sound of ppht.

"...And that, Cady, is why I had this book shelved as fiction!"

Here's some silly and lighthearted word vomit from an idea that kept bugging me for months.