Sunset let Flash and Applejack help her to her feet once the world stabilized to her senses. Her head throbbed, human tissue and nerves sore from the energy that had pushed through it...and from what still bombarded it. She rubbed her face, trying to get her eyes to focus properly, to give her more than a blurry world of color. “...Is...everyone okay?”

“We’re fine,” AJ responded. “Only one ta collapse was you, Sunset. Ya gonna be alright?

Steadying herself, Sunset nodded. “Yeah...I...think I’m okay.”

“Good! What happened, darling?! One minute we were playing and the next, it was like...” Rarity’s voice trailed off.

“Like you were calling us for help,” Rainbow interjected, landing lightly on her feet, wings folding neatly against her back.

Rarity nodded, brushing a lock of hair away from her horn. “Yes, like that...and it was as if the magic answered that, without us trying.”

“It felt like the Fall Formal,” Fluttershy murmured, “when we jumped in to protect Princess Twilight.”

The connotations were concerning, and raised more questions than she had answers for, particularly since as far as she was aware, she...didn't represent an Element of Harmony...did she? Sure, without Princess Twilight, the girls were representing the incomplete set, but the only one remaining was Magic, and whatever she was tapping into didn’t feel at all like the Element of Magic. Was it possible there was a seventh Element? Or had her exposure to Magic’s power simply left a way for her own magic to connect to the Elements, like rainwater making use of an old, dried up riverbed to flow towards a lake?

Sunset tried to marshal her thoughts, to bring the wildly racing mess under some measure of order and control. She had to do damage control in the now before she could focus on what ifs. “...right...okay. We need to figure out if anyone was affected by that burst.”

Applejack snorted, guiding her to a chair. “Ah’d say things were affected alright.” Sarcasm dripping from the farmer’s drawl was a bad sign. “Think ya better sit fer a spell afore ya start takin’ stock o’ that.”

Still scrubbing at her blurry vision, hoping the rest of the light induced spots would fade quickly. “How bad is it?”

Something square and wrapped in waxed paper was pressed into her hands. “Here, darling, eat this. These were sent along for magical refreshments, correct?” The scent of the energy bar hit her nose and the redhead unwrapped it so she could take a hurried bite out of one of the ‘Little Sun Bites.’ “In fact, in the face of whatever that was, would it be prudent for all of us to have one?”

“Yes,” Sunset responded after she swallowed. “Even if you aren’t ponies, your bodies are housing and expending Equestrian magic, which they are adapting to on their own. Better safe than sorry—magical burnout is dangerous. That's what happened to me after the fight with the Sirens.”

The sound of wrappers being pulled open and people chewing filled the silence, at least until Pinkie spoke. “Speaking of burnout, the lights in the hall are toooootally busted....”

Flash snorted. “According to the text I just got—my cell phone is fine, by the way—the power is down across the school, and everyone saw the rainbow light show. I’ve sent out the word that it wasn’t because of a fight against another monster so no one panics.” Sunset could make out him shaking his head now. “You girls sure don’t do anything by halves.”

The former unicorn leaned her head back, already dreading talking to Miss Luna and Principal Celestia over this magical mishap, when her recovering eyesight noticed something odd. “Um...if the power is out in the school, why do we still have lights in here?”

“Yeeeah, that’s one of them things that was affected,” Applejack responded.

Now that her eyes weren’t still dealing with spots, Sunset let her gaze turn straight up. Where there had been cheap fluorescent lights, now polished crystal mage lights hung from the ceiling, giving off the familiar glow she remembered from Equestria. “Sweet sunfire, how in the name of Celestia’s golden horseshoes did we do that?!” Her eyes started looking over the room, and other changes jumped out at her. “The principals are going to kill me,” she groaned.

First were the crystal mage lights, which she realized were made of the clear crystals that grew in abundance beneath pegasi cloud cities. These crystals held lighting enchants easily since even in a natural state they tended to glow from within and something about their formation close to the rainbow falls that fell from the cloud cities meant that light threw out rainbows of its own. With the right enchantment and a skilled artificer, they could be coaxed to shine light in any multitude of shades and hues.

The next change she noticed was the cabinet that she had been using to store things in. Gone was the simple particle board and plastic, replaced by a thing of fine, rich wood with golden and crystal inlay, done in the gentle swirls and designs so often found in Equestrian furniture. One of the doors was open, and as she leaned to look, she realized that the short space of cubby holes was gone, replaced by something far larger than its outside. At her best guess, it was about two thirds the size of the room they were occupying, with an external footprint comparable to the wardrobe cabinet she had in her loft. Sunset’s eyes widened—that was one seriously high end expansion spell on top of transmutation! By all rights, it should have been impossible.

Ignoring her headache, she extended her senses to feel the cabinet’s magic, and recognized the the lingering touch of transmutation, as well as a spatial expansion spell as powerful as something Celestia could have cast...and a third spell, one she recognized: a locking spell, like what unicorns used, that could be keyed to either a magical signature or a physical key. Sunset took another bite of the energy bar in her hand, dwelling on that for a long moment, before realizing the cabinet wasn’t the only source of high end magic in the room.

The door to the hall might as well have been a beacon, and she turned around in the chair to stare at it over Rarity’s shoulder. Like the cabinet, the cheap human metal painted door was just gone, replaced with a door that would have fit in in the Canterlot Palace. In fact, it was exactly like the door that granted access to the relic room, where Celestia tended to keep powerful or dangerous artifacts. The wood was from a special breed of hardwood that only grew in the Everfree forest, soaked in wild magics throughout its life, and the crystals inset were a mix of powerful stones for warding and protection, including a dozen small Nightstones, a smattering of fire rubies, some sunfire crystals, and a single polished disc of a striated green stone that was only native to the lands claimed by the fox-folk, that they called an Eye of Inari after their progenitor deity. They were worth a small fortune in pony lands, meaning very few could make use of their properties that disrupted illusions and shapeshifting spells. She had grown up seeing them though—most of the secure parts of the palace had one set into the doors just like this. Even the normal door knob was gone, in favor of a gently curved protrusion and flat crystal faceplate that held a small keyhole and thrummed with the magic of a powerful locking spell.

Rainbow nudged her with an elbow, before gesturing with a hand holding a half eaten energy bar. “That’s one hell of a door. Is that what passes for one in Equestria? Cuz holy shit, that’s a lot of rocks. And is that real gold?”

“Yes, the ‘rocks’ are for wards, and yes,” Sunset responded, getting up to inspect the door closer. “In fact, this is almost identical in structure to the doors in the palace...which means...” She placed a hand on the crystal plate, feeling a tingle of magic go through her arm. There was the sound of a complex mechanism coming undone, and she could feel the wards relent. With a gentle tug, the door swung inward on silent hinges. “It's not just a key lock. It’s keyed to magic signatures...and if I was a betting pony, I'd say it's keyed to our magic signatures.”

Without thinking about if it were even possible, Sunset dropped to one knee, and touched the tip of her somehow still present horn to the door, calling to mind one of the old diagnostic spells she had learned. It was a struggle—her headache intensified and it was like pushing molasses through a drinking straw—but a little tendril of magic wove into a spell.

“Uh...Sunset? What’re ya doin’?”

“Diagnostic spell. One second.” By the time she had finished, she was sweating and red faced, and her head felt like it was splitting open, but she had her information. Rainbow helped her up and offered her another energy bar, which Sunset practically inhaled. “So, good news? The door is keyed to the six of us, and there's a key mechanism too so if we can find the key that fits it, we can give it to people we want to grant access to the room.”

Flash raised an eyebrow. “And the bad news?”

The former unicorn reached up to rub the base of her horn with a wince. “I won't be able to cast anything here more complex than what I just did, unless something makes this body adapt a lot more to using my normal magic and not...whatever causes the pony-ups....and also, by all the fundamental laws of magic in Equestria, the transmutations in this room are impossible. These are permanent transfigurations of entire objects on a grand scale, with complex enchantments woven into their very being. None of that should be possible. Even the princesses can't do this...”

The girls all looked at each other, unsure, before Rarity cleared her throat. “And yet, we seem to have made it possible, darling. You’ve said the Elements are extremely powerful and it's their power we are drawing on. Is it possible they exceed some kind of power threshold that makes them capable of doing this?”

“It’s possible, I guess? Nopony is really well versed in the Elements and their limitations. They’ve historically only been used sporadically against major world ending threats, not summoned on a daily basis for band practice.” Sunset stepped through the doorway to see if any changes extended to the hallway beyond.

In that moment, now out of the room, she sensed what she had missed because she had been inside its effect. The redhead whipped around, ignoring the way her head protested and her vision swam dizzily for a moment. Gritting her teeth and forcing herself to focus despite how much it hurt, Sunset cast another diagnostic spell. Her concentration wavered several times, from the sheer pain in her head and the way her human body was protesting against using magic the way she was forcing it to, but she persisted, digging her metaphorical heels in and pushing on through it. No one else could do this, so she had to.

“Oh horseapples,” she swore, as she analyzed the magic enveloping the room. Somehow, without trying, they had fashioned an extremely powerful ward on the space. “Moldering, reeking, waterlogged horseapples!” Agitation was joined by borderline panic. These weren’t just simple effects. Permanent transmutations, powerful enchantments, and an entire room warded more strongly than even Princess Celestia’s own chambers...and Sunset was at a loss to explain any of them.

“Okay...okay...” she muttered, running a hand through her hair. “Think, Sunset. We can deal with this, it's just a matter of how we present it. I mean sure, the wards are permanent, but at least this way our experiments should no longer affect the rest of the school....” The cold air in the hall was making her nose run again, and she wiped her face with the back of her hand to get rid of the dampness under it.

“Sunset?” Rainbow’s voice was nearby, but still distant and buzzy.

Her ears flicked back and she shook her head out of habit, only to regret it when it sent a spike of pain through her skull. An involuntary noise of pain escaped her, before she resumed her self addressed train of thought. “It solves the storage problem for the gems too, since the cabinet is warded too, and I can just pay for a replacement out of pocket in a few years and take the enchanted one with me...”

The unicorn-turned-human looked up into the worried faces of her friends. “It’s okay, girls,” she reassured. “It's nothing that will hurt anyone...”

“Um...Sunset, that’s not...it's just that...” Fluttershy started to say, trailing off, sounding like she was talking from the other end of a long tunnel and not from a few feet away.

“Yer bleedin’, Sunset,” Applejack told her bluntly. “Thinkin’ ya need to stop an’ siddown fer a spell.”

Sunset resisted the urge to shake her head, wiping her nose again. “Bleeding? I’m not—” she began as she took a step forward, only for the world to tilt disastrously to one side.

“Sunset!” cried a chorus of voices.

Warm hands caught her, and she felt herself being lifted. The world spun and she closed her eyes to avoid revisiting the food she’d eaten. “It's okay, pony-girl, we’ve got you,” Flash’s voice echoed near her ear.

Resting her sweaty forehead against a familiar shoulder, the redhead tried to protest the fact that her ex-turned-friend was carrying her through the hall. “Flash, you can't. People will—”

“Can and will, Sunset. The nurse needs to look at you, let people think what they want. You know the truth. Your friends know the truth, and so do I. Besides, what would Twilight say if she found out we just let you collapse in the hallway?”

Her brows pinched as her mind went to her dorky girlfriend first, imagining the shorter girl with her hands on her hips, giving them all an imperious glare. A tired laugh escaped her, one she regretted since it renewed the pounding in her skull. “...she’d be furious...” she mumbled.

“Right. And I don’t want a magical pony princess mad at me,” Flash concluded.

“To be fair, darling, we’d be rather cross with ourselves,” Rarity’s voice interjected from somewhere in the vicinity of Sunset’s feet. “That’s why I’m accompanying you both to the nurse, and why, other than Fluttershy, the other girls are going around school to see if anything else was affected by our little magical...accident.”

“...don't need a nurse. Just...pushed a little hard,” Sunset grumbled. “...I’ve dealt with surges....and...a little feedback...before.”

Rarity made a loud sound of disagreement as the shifting bounce told Sunset she was being carried down the stairs. She could also feel Flash’s heavy sigh. “Sunset,” he told her when it seemed Rarity wouldn’t, “you turned grey, and you didn’t even notice you had a nosebleed.”

“Yes, darling,” Rarity agreed. “It was quite dreadful, really. None of us has ever seen you faint before and it was...unsettling. Please humor your friends who thought for a moment that you had seriously damaged your health, and let the nurse make sure you are alright.”

The redhead tried hard to organize her somewhat scattered thoughts, wanting to explain that the situation was not near as dire as they thought, that she had dealt with plenty of episodes of both magical over-expenditure and the pain of thaumic backlash in her life, but her head gave a warning throb that felt like knives being driven into her brain by way of her eye-sockets. The agony caused a whimper to make its way past her lips, her world twisting and rolling despite her eyes being shut.

“...nset?” The wave of pain subsided slowly, but it left her nauseated and dizzy, and Flash’s voice sounded hollow and far away.

“...nurse...might be good... Feels like somepony...kicked my horn...at the base...” she slurred.

Cool fingers brushed her forelock back. “You really aren’t in any kind of state to argue, Sunset, but I am glad you’ve chosen to acquiesce. I am truly worried about you—you look positively ashen.”

Sunset felt every single one of the twenty two steps in the stairwell like a blow to not just her brain, but also to joints that hadn’t ached and burned this badly since the week after the formal. Her jaw clenched and she swallowed reflexively, desperate to keep her stomach from redecorating everything in the immediate vicinity.

Their arrival at the bottom of the steps was met with sounds of two voices: the principals, each expressing their dismay at what they saw in different ways.

“Sunset! What happened to her?” Prince—Principal, she corrected her mind aggressively despite the pain it caused—Celestia sounded extremely worried.

Her sister, on the other hand, defaulted to dry wit. “I see my first thought that this was another of Miss Dash’s juvenile pranks born of ego was incorrect. You appear to be in quite a state, Miss Shimmer.”

Sunset groaned in response, but Flash grew briefly incensed. “You jumped right to Rainbow Dash pulling a prank? Isn't that a bit...” he trailed off, and an awkward silence ensued. It ended when Flash’s shoulders slumped. “Never mind. My bad. I realized what I said as soon as it came out of my mouth.”

“Indeed. Now perhaps you can explain on the way to the nurse, Miss Belle, Mister Sentry. What happened? Power is out over the whole campus.” Luna’s tone remained brisk, but Sunset could hear the concern layered in the cool, controlled delivery.

Movement resumed, and Principal Celestia added, “We also saw...and felt...whatever that was. I...can't recall anything quite like that before.”

“...’S the Rainbow...of Ligh’...” Sunset mumbled. “Element’s...true power...”

Rarity patted Sunset’s shoulder this time, her voice now near Sunset’s head. “Rest, darling. Save your strength.” Then she cleared her throat, addressing the adults. “Sunset calls it the Rainbow of Light—I assume that’s the Equestrian term for the magical rainbow our magic seems to summon at its most powerful. As for why it happened...none of us are quite sure. We were doing our band warm up, with Sunset’s new instruments monitoring everything, and...I think Sunset’s magic reacted to something. At least, it started with her, but it was as though her magic called to the rest of us, and the magic within us jumped to her aid.” The designer sounded puzzled by her own explanation. “It was as if she were...calling for help, as preposterous as that likely sounds.”

Flash cleared his throat. “I think she saw something. Some kind of...vision...or something. Right before it happened...Sunset got this look on her face. She was...”

Oh horseapples, Sunset whimpered internally. Please don't tell them I was like a spooked little filly.

The young man carrying her down the hall paused in his words, thinking. “It looked like it freaked her out,” he finished. “That's when she did the pony thing, and her horn started glowing red.”

The former unicorn struggled to provide some form of coherent explanation, to clarify Flash’s...fairly accurate guess. “...nightmares...about dark magic...made me twitchy...all day...caused a surge...” She pried her eyes open, wincing as the added cerebral input made everything worse. “...sorry...about the room...and the lights...”

“Dark magic?” the women chorused, before Celestia took charge. “Is the school in danger?”

“...don't think so...?” It hurt to think. Sunset couldn't answer until something was done about this headache. “...sorry...head’s...muzzy. Hurts.”

Flash adjusted his hold. “We’re almost to the nurse, pony-girl....and look on the bright side—your nose isn't bleeding anymore? You still kinda look like you lost a fight with the Hulk though.”

Pained as she was, she felt her lips turn up at the edges. “Heh. I...understood...that reference.”

Nurse Redheart, for her part, was not exactly the most sympathetic woman when they arrived, chiding Sunset, “Just because you provided me with first aid instructions for ‘magical’ injuries was not carte blanche to go and take foolish risks, Miss Shimmer.” Despite that, her hands were gentle as she gave the former unicorn a once over.

“Sorry,” Sunset managed. “Can I...get something...for my head?”

The nurse shined a penlight at each of her eyes, making a thoughtful sound. “Tylenol only, I’m afraid. If I hadn't seen the same light show as everyone else, I’d think you had a concussion. As it is, the material you provided suggests that...'' she leaned over her desk, flipping through the binder that Sunset had put together, “...’thaumic backlash’ shows symptoms not unlike both a concussion and heat exhaustion.”

Sunset sighed, knowing the woman was right. “...yeah...”

“Then you need to take it easy for a few days. No gym class for the rest of the week, and I recommend you take tomorrow off from school entirely to rest.” The woman passed her a paper cup filled with water and a couple of white pills. “Two Tylenol now for the headache, and you can have another two in eight hours if the pain comes back. No aspirin or ibuprofen for at least twenty four hours. And I want you to consider drinking at least a full bottle of water before you leave here this afternoon. How's your stomach?”

Less likely to turn itself inside out all over the floor now that Sunset was laying on one of the beds in the nurse’s office, if she was honest, but that felt like too many words, so she settled on, “Better now.”

“Good.” Redheart addressed the rest of the group. “Let her relax here in the dark and quiet for a little while. You can talk outside—she’s not going to be able to answer a lot of questions until she's more coherent. I’ll monitor her in the meantime.” She shooed them along, and settled back into her chair, going back to the binder Sunset had made.

Medicine taken, Sunset laid back and let herself drift, worry pulling her mind back to what she had seen. There was dark magic and it was coming for Twilight Sparkle.

And she had no idea how to stop it.

So yeah. You were all wondering what happened. Now you know. Lots of impossible shenanigans, but hey, at least Sunset now has a place to store a fortune in gemstones?

Furthering the world-building, I liked the idea that ponies solved some of the same puzzles humans did with applications of magic and magical objects--like the lights. We see evidence that ponies have a lot of the same practical amenities that humans have, but without the same kind of tech/infrastructure. Even Ponyville, as remote as it is, seems to possess lighting at night that isn't fire/lantern/candles, but there are no powerlines and nothing to indicate that they use electricity the way we do. So I solved the problem with magical crystals, ones that could be crafted by a pony with a gift/talent/mark for it and thus traded to others or installed in homes and businesses. In fact, such artificing and enchanting is a steady part of the Equestrian economy in Rubicon, where the most common things are just as ubiquitous to them as lightbulbs and toilet paper are to us in first world countries, and even the really nice, expensive things can be found in the right place for a price. It gives them a much richer economic structure, and one that is much more fitting for the ponies, where magic is as natural as breathing to them, and there are very likely ponies with talents that lend themselves to things like making enchanted objects, or preparing crystals for magic, or any number of other skills that humans would never develop but that would be crucial in a magic based society.

Along those same lines, I did work on the other 'races' of Equestria, and how many of those would interact with not just magic, but ponies in terms of trade and the crafting of objects or the use of raw materials. Which races have active spell casters, what skills or gifts are otherwise inherent to a species, etc, which is where the bit about the fox-people stone came from. Maybe I should do a blog breaking down the various races and their general strengths. That might be cool, lol.

So yeah, Sunset had a vision, and blasted her own school. Oops? But hey, now they've got a special magic practice room. And she's now aware that SOMETHING is looking at her girlfriend...but the question is what/who? And what can she do to stop it?

*dramatic music intensifies*