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“You keep looking that over,” I said to Starlight, who was staring at the chalkboard equations for the millionth time today. “Why do you keep looking that over?”

Starlight frowned. “I don’t know. Something just feels off.”

“Starlight, we checked and double-checked our math, and then we double-checked our double check. Even Star Swirl double-checked my double check of our double check!”

She didn’t seem convinced, but math never lied.

“Starlight, you can stop worrying.”

My eyes gravitated to Sunset and Luna in the middle of the room. Around them wound a series of chalk lines, scrawled outside the original Dream Dive glyph. They glowed a full spectrum of colors, and their magic tingled like windchimes in my ears. Even at this distance the arcane charge tugged at the individual hairs of my coat like static electricity.

A battery glyph, as we’d so aptly dubbed it. That was to say, rather than the more academically correct “séance circle” I had initially christened it. I wasn’t fond of such a straightforward name, but I was outvoted two to one. Apparently, being a princess still only counted as one vote. Not that I was disappointed or anything. Because I wasn’t.

Regardless, the, ahem, battery glyph acted just as its name implied, like a battery meant to power a spell. Thanks to some ingenious surge crystal work and a little more cleverness besides, we figured out a way to make use of the Dream Dive Spell’s latent feedback, allowing the circular nature of magic to replenish itself. To a degree, anyway—Conservation of Energy still withstanding.

Effectively, it let us take turns powering the Dream Dive Spell, freeing us up for some important continuing R&D. Or some much-needed R&R, as Starlight all too readily put it, like the chocolate chip cookie I nibbled on from the steaming plate Spike brought in a minute ago. It was as soft and gooey and delicious as the way Mom made them.

Starlight shot me a look. “Me stop worrying? Twilight, you’re the princess of worrying. We named a verb after you. The fact you’re not worried has me worried.”

I rolled my eyes at that. “Twilighting,” as they so wonderfully called it, still didn’t sit well with me. It felt… presumptuous? I didn’t know what to call it. Still, my friends were my friends, and they wouldn’t be themselves without acting true to who they were. Sometimes, that meant getting a verb named after you.

But that was whatever. It was hard to feel concerned for the world while munching on a little bit of heaven. Maybe that’s why Mom made me cookies all the time when I was growing up. I shook my head. Getting off track.

All the same: “Starlight, we did the math. I did the math.”

“I know, it’s just… I have a bad feeling about it, Twilight. Like, I don’t doubt you did the math right, but… what if we were fundamentally wrong about it? Or there’s things going on in the dream that we can’t account for? Sure, your logic is sound leading from one thing to the next, I mean both me and Star Swirl believe that on a personal level. But what if the whole basis of your equations is off?”

“I get that you’re worried, Starlight, but Sunset and Luna are counting on us. We’ve made it this far with our hypothesis and theories holding up. We can’t go back to the drawing board now. I mean, we could, but everything’s working exactly how we predicted. And honestly, if what Sunset said is true, we don’t have time to start over.”

My words didn’t seem to comfort her much. She wore that slant of a frown that meant her gut didn’t agree. The cookie in my mouth suddenly wasn’t as appetizing as usual. Not only did I hate seeing my friends in a mood, but Starlight had a pretty good track record when it came to gut feelings.

I put a comforting hoof on her shoulder. “Let me grab our notes and we’ll go over our dream dive theory from the ground up. How’s that sound?”

And there was the smile I hoped for. She squeezed my hoof and gave me a playful bump with her shoulder. Her smile went rogue, and in a flick of her horn she absconded with the unbitten half of my cookie.

“Hey!” I said. “The plate’s literally right over there!” I jabbed a hoof at it halfway across the room.

“Yours was closer.” She gobbled it in a single bite and with her mouth full continued, “And the little pouty face you make is priceless.”

“I do not make a pouty face.” I made due effort to keep my lower lip exactly where it was supposed to be.

“Uh-huh,” Starlight said, pulling my notes from the far table and arranging them into neat little stacks for me to take. “Sure you don’t.”

The grin she shot me I had once heard Applejack call “slappable,” and although I abhorred the idea of hurting my friends, I couldn’t disagree on a metaphorical level. Channeling that bit of Applejack, I gave her an eyebrow as I snatched my notes from her, reordered them to my liking, and led her out.

We took our session to the library. I appreciated the freedom the battery glyph gave us, but that constant magical hum bored into my thinking space and I had to get away from it if we were to really dig into this the way Starlight wanted.

“It’s crazy that just a bit of chalk can do so much,” Starlight said on our way there.

I tried my best not to wince. Yeah, about that…

I hated this glyph. I hated it. The magic was fantastic, no doubt, but… I couldn’t get past the fundamental truth of its creation. Just thinking about it made me queasy.

This wasn’t regular sidewalk chalk that foals played with. When it came to magic, that kind of chalk did quite literally nothing. The only “chalk” that had magic-conducting and magic-insulating properties was actually ground unicorn horn—donated by willing ponies, of course, after they passed. Like donating a heart or a kidney. Still, it didn’t make drawing out those lines any easier.

Starlight and Sunset had no idea, thankfully, but it didn’t get past Star Swirl. He recognized it the moment he first stepped through the door. That was… a long conversation he and I had later that night. After dealing with Starlight’s cutie mark magic, though, I believed he came to terms with this much easier. He’d… sobered up to our situation, and seeing the next shipment come from Celestia herself probably held a lot of water.

This was ethical gerrymandering at its finest. To call it anything else would be an insult to those generous enough to donate their bodies to science. But where this sort of magic was normally associated with the insane and occult, here, we used it for the safety of Equestria and the wider world beyond. I had to keep telling myself that.

“We’ll take whatever advantages we can get,” I said.

Spike had finished reshelving the returns sometime that morning, which gave me one less thing to worry about. I really had to give him a big Best Assistant Hug later. He’d always been instrumental to daily maintenance around the castle, but keeping up with it through this ordeal helped me stay focused and stop sweating the small stuff, as Applejack put it. Even with the fate of Equestria hanging in the balance, life still went on. And that meant ponies visiting the library to check out a book or two from time to time.

We set up camp in the back nook, where Luna had first found me and set this whole chain of events in motion. Call me a dreamer, but I liked to think that sort of full-circle poeticism applied to real life.

Or that was just confirmation bias working its evil machinations. Sometimes, it sucked being both a literary connoisseur and a science nut. Empirical evidence and literary synchronicity weren’t the best of friends.

I cuddled up beside Starlight to make use of her body heat. It was rather temperate outside for a fall morning, but the crystal castle tended toward the colder side, even in the summer months. Besides, I liked being near her. She had a certain gusto about her that I’ve tried absorbing via proximity over the years. Learning went both ways, and as a teacher I’d be a fool not to take advantage of that.

“Okay,” Starlight said, levitating a dozen books into an orbit around us. “So starting from the top, we’ve got a Mindtap Spell as the foundation for our spell. And we amplify the mental presence of the diver with a Clarity incantation.”

“Right,” I said. “Which is possible because we let the Mindtap bear the initial load of the cast before Clarity comes into the picture.”

I loved seeing her get like this. This deep thinking she did when we went over magical theory and spellcrafting. There wasn’t really another pony out there that was into this stuff like I was, minus Star Swirl of course. We were kindred souls on the quest for knowledge.

“And Waterwalking as a means of physically injecting the diver into the dream,” Starlight continued, “with the capacity to interact with it, but we maintain delineation by channeling the spells from different sources—Waterwalking from Star Swirl, Clarity from me—so that the magics only interact at discrete intervals, which you maintain by enforcing a steady state via the original Mindtap.”

“At a one-to-three ratio, yes. Still all correct.” I nodded my head along with her breakdown of our spell. By this point, every aspect of it seemed rote and ordinary. Foal’s play. I couldn’t see where she was having issues with the spell’s logic.

She tracked a particular sheet of looseleaf as it passed in front of us. “The spell itself is grounded in the diver’s cutie mark, which also acts as the anchor and where the spell actually takes place, because it’s the only part of a pony that can handle that kind of magical throughput without things getting all explodey.”

“Laymare’s terminology,” I said, “but yes.”

“Hey.” Starlight shot me a grin. “That’s how Sunset phrased it, and now I refuse to call it anything else.”

“Laymare’s terminology,” I reaffirmed with my own grin. “But yes.” We shared a laugh.

She leaned into me, and the weight as I pressed back was both reassuring and fulfilling. I could have stayed like that all day.

“And that’s… that’s the spell.” She tapped her hoof on the cover of a book in front of her while staring at the flurry of notes encircling us. “I just… I don’t know. It just feels off.”

“Care to explain?”

“That’s what I’ve been trying to find the words for… questioning everything we’ve done and have yet to do is… I, I just don’t want to sound stupid.”

“Starlight, there’s no such thing as a stupid question. And asking them doesn’t make you stupid. Asking questions is how we learn what we want to know and how we affirm what we do know.”

I caught myself frowning before she saw it, but I couldn’t shake the mood it put me in. How could she think that about herself? About asking questions?

Starlight scratched the back of her hoof, and she wore that slanted mouth that always worried me. “Like, are we sure it’s actually using the cutie mark, for instance?”

“It’s what all our research has so far pointed to. And you said it yourself when we were developing the concept. I don’t mean to dredge up the past, but you’re the cutie mark expert.”

No matter how gently I brought it up, Starlight winced as I said it, and I felt terrible. “I mean, I get that,” she said. “And I do think we exhausted every angle we could. But… what if that’s not how it works? Or if that’s not how it works anymore? What if there’s more to it than we thought or could possibly expect? How do we know for certain the spell’s contained solely within her cutie mark? How do we know it’s not flowing through all of Sunset’s body instead?”

I was silent for a moment.

We designed it to work within the confines of her cutie mark, but the truth was, we had no way of verifying that outside of things not “getting explodey” yet, as Starlight put it. The conclusion of our experiments determined that it did indeed originate there, but like she seemed to worry, it didn’t rule out the possibility of a metastasis of sorts.

But it worked, and as much as it went against all I knew as a scientist, working with multiple unknown variables was all we had. And if I were to allow myself that one kernel of hope, we didn’t have any evidence that disproved our theory.

“What about the Tantabus?” Starlight asked.

I blinked back to reality and focused on her words. “What about it?”

“Well, we thought it was the reason why she was so much better at dream diving than us, because it gave her some unknown connection to Luna. And maybe that was true initially, but she gave the Tantabus to the Nightmare a while ago, and her dreams have only been getting better and stronger and more vivid, if what she’s said tells us anything.”

“She’s in Luna’s dream with Luna. I admit I don’t understand it, but that’s all we have to go on.”

“Or maybe she’s getting better because she’s expanding her ability to utilize more than just her cutie mark?”

I got that uncomfortable, squirmy feeling in my gut like Starlight might be on to something. “She’d tell us, I’m sure.”

“It’s dream magic, Twilight. She might not even be aware of it, if that’s the case.”

I… that I couldn’t argue. The nuance of certain types of magic could be complicated enough before factoring in something as variable as consciousness. Dream magic still very much belonged to Luna and Luna alone. We knew very little about it.

Cutie marks, the Tantabus… so many variables we simply didn’t have the tools or understanding to figure out. Educated guesses were all we had to go by, and thank Celestia we’d been right enough so far.

It got me thinking about my own Tantabus that I apparently had inside me. I still didn’t know what to make of what Sunset said. I believed her, though. I couldn’t ignore my own fears, especially not while urging others to face theirs.

I had to face mine, too. I had to keep going, even with the looming, ever-present fear of making things worse.

“It’s gotten us this far,” I said. I swallowed and put my hoof on Starlight’s. “It’s the best we’ve got right now.”

“I’m just afraid that everything’s going to blow up in our faces sooner or later.”

And there I definitely had something reassuring to say. I smiled and squeezed her hoof. “Which is where your magic comes in. Just like we practiced.”

“But if it really is using more than just her cutie mark, I don’t know if my magic will end the spell.”

And there went the wind from my sails.

“I’m just…” Starlight sighed. “There’s just too many variables that we’re trying to tackle with hard science. Like you said, it’s gotten us this far, but I’m afraid we’re moments away from all Tartarus breaking loose.”

And as if her words were the law of some divine being, a deafening boom ripped through the castle and drove my ears flat against my skull. The windows shattered inward and rained down on us. I felt the tiny pricks against my skin before I found the presence of mind to throw up a bubble shield.

Starlight and I shared a horrified glance, and we booked it back to the portal room. The stink of burning rubber and ozone hit me like a brick wall as we burst through the double doors. My eyes watered from the intensity.

Star Swirl lay unmoving a good twenty feet from the glyph, and a glaring light whitewashed the room. What looked like a tree—pure white with the faintest hint of blue around the edges—had sprung forth from the glyph encircling Sunset and Luna. Except to my horror it wasn’t a tree. It was pure, unfiltered magic screaming, arcing, clawing out of whatever confines previously contained it.

“What’s going on!?” Starlight yelled. She ran to Star Swirl’s side to check him over.

Starlight had Star Swirl covered. I had to figure out what was going on with Sunset and Luna, but I had a horrible gut feeling I already knew.

The very Something we feared had happened—the Something we hadn’t planned for, the Something we knew nothing about.

We’d been spared an immediate backfire thanks only to the battery glyph, which seemed to be damming up the flow of magic. It wouldn’t hold long, though, judging by the glowing cracks spidering outward along the floor.

My mane flapped wildly around me in the hurricane winds as I struggled to get near. Errant bolts of magic tore scars along the crystal floor that I had to dodge or risk becoming a pylon and conducting all this rampant magic through me. I didn’t want to think about what that might do to myself or the castle.

Instead, I focused on Sunset and Luna. I had to get to them. I had to stop this.

I had to charge up a bubble shield to step over the glyph. The rampant magics warping around the shield turned bright green like copper ablating in a fire. Within the perimeter of the glyph, all was stunningly quiet.

“Twilight!” Starlight yelled as she slipped in behind me with her own shield. She seemed momentarily surprised by the silence, but regained herself.

We joined our shields into one, and she came in for a hug. Her coat was scorched down the side, the hairs around the edges still curling. The skin beneath looked ready to blister.

“Oh my gosh, are you alright?” I asked.

“I’m fine.”

“And Star Swirl?”

“Unconscious, but breathing. He’ll be fine, but we need to get a lid on this now.”

“Right,” I said. “Just… just stick to the plan.”

Just stick to the plan. Starlight was scared. It was written all over her face. But that was okay. I had faith where she didn’t. Everything would work out the way we planned. I believed in her, in us.

She closed her eyes and hefted her half of the bubble shield onto my shoulders, focusing all her attention on her cutie mark spell. Her mane went weightless in the latent magic, and for a moment, I held my breath. Sunset’s cutie mark took on Starlight’s spearmint-green hue and peeled away from her flank like a sticker. It floated aloft between us before popping out of existence, and…

And the storm continued.

“But…” I said. “But the spell—”

“Twilight,” Starlight said. There was fear in her eyes. “Forget the spell. Forget our plan. It’s just like I was saying. Somewhere, somehow, we were wrong! We were wrong the whole time. Our research, our hypothesis, all of it. The spell’s been using her as its anchor, not her cutie mark. I… I can’t stop this.”

No. No no no… This was all wrong. It shouldn’t be happening. It couldn’t be happening! We did the math. I did the math! I could hardly breathe.

“Twilight!”

“I know! I know!” How did we stop this? What kind of magic was this? Did I plop a Containment Spell down around them and hope for the best? But that would kill them…

And as if that wasn’t the worst thought to run through my mind in my lifetime, another reared its ugly head. Which was worse: them, or all of Ponyville?

I… I… No, I couldn’t let them down. They were counting on me.

I cast a quick Scrounging Spell to tap into the energies forking around us. If I were to undo this, I’d have to know what kind of magic it was first.

As I focused on the ebb and flow, I started picking up the loose threads. There was a pattern to it, as jumbled as it was, and—

Something touched my hoof. I gasped and jerked backward.

It was Sunset. She reached out again and rested her hoof against mine. Her eyes were cracked open, and she slowly raised her gaze toward me.

The spell wasn’t just falling apart. Sunset was waking up.

That was it. This rampant magic wasn’t just breaking the dream dive, it was piggybacking on Sunset’s Wake-Up Spell.

But that would mean…

The magic within the chalk circle crackled with lightning and bled outward like lava, forcing Starlight and I to huddle farther inward. It radiated an angelic white light, laced with threads that spanned the full spectrum of the rainbow. Outside the glyph, cracks spidered along the floor and snaked up the wall to catch a tapestry on fire.

I was petrified. Here on the precipice of a cataclysm, I didn’t know what to do.

I was terrified of making things worse, but doing nothing would be just as catastrophic. I remembered back to what Sunset told me. I had to be true to myself. I had to keep doing what I thought was right. Educated guesses were what got us this far, so I put my faith in Sunset’s wisdom and made another.

I knelt down beside her and lit my horn.

She put her hoof on my cheek, and I held it there, feeling the tears well up in my eyes.

“I’m sorry,” I whispered, and just as Sunset seemed to wake fully, I pressed my horn against hers and let the spell go.

Her eyes unfocused, and her face sagged as if all her energy melted away. She closed her eyes, and her hoof fell to the floor. The magic storming around us died away to leave me in a profound silence that seemed so distant yet so smothering.

Another hoof touched my shoulder—Starlight this time. She threw a hug around me and said words drowned out by an intense ringing in my ears. I felt what might have been her tears seeping into my coat.

Like the silence, she seemed so distant. Everything but Sunset seemed so distant.

Sunset. I couldn’t get it out of my head. I knew that look in her eye. It was the look of a mare begging for help, a mare that needed the comfort of somepony they trusted beyond any shadow of a doubt, a safety only I could give.

And I had cast her to the wolves.