When Rarity left for the boutique in the morning, Twilight was still buried deep in the lab, mumbling to herself and nudging glowing particles with her horn, taking furious notes. By the time Rarity returned, it was obvious Twilight hadn't slept a single wink.
"Hi, Rarity!" Spike said, meeting her fresh-faced in the kitchen. "How was your day?"
"Actually it was marvelous!" Rarity replied, putting the final touch on a fancy tomato sandwich. "I sold a gorgeous white wedding gown to Bon-Bon and took in commissions for no less than ten mares needing outfits for the gala next month."
"Sounds busy." Spike grabbed a pawful of small gems from a snack box and munched them slowly. "Are you ready for tonight?"
Rarity nodded. "As ready as I'll ever be."
"Awesome!"
They descended into the basement lab. Twilight was moving slowly but with purpose, heavy circles under her eyes. Spike bounced ahead and glided around the lab, gathering equipment and reviewing notes.
"Here's your instructions," Spike said, passing one of the scrolls to Rarity.
"I've determined a few parameters that will help make sure you have a smooth entry into the construct," Twilight said, shaking the bleariness out of her voice.
Rarity read over the checklist as she chewed the last bite of her sandwich. "Mhm… Mhm…" she muttered. "Well it's a little more in-depth than I was expecting but everything seems reasonable."
"The most important thing is to go with the flow," Twilight said. "If you disrupt the network too much it'll kick you back out, but if you don't focus in deeply enough then you won't be able to get a detailed look at the finer workings."
"It's kinda like sticking your face underwater," Spike explained. "If you do it carefully you won't scare the fish away, but you also need to make sure you have the right goggles to be able to see them."
Reading the checklist again, Rarity nodded. "Right."
With a burst of energy, Twilight hustled around the lab in a flurry of final preparations. Spike guided Rarity to a small chair near the pulsing cloud of magic. Within minutes, everything was ready.
"Okay, here goes," Twilight said, bringing over what looked like some kind of helmet-shaped fitting for a unicorn horn. "I've tuned the focusing runes to match your magic better, so hopefully you'll be able to dive pretty deep. Remember, you'll go into a sort of trance as your magic melds with the field, but we'll be here for you, monitoring everything. Ready?"
"Ready," Rarity replied. She kept her voice steady, but the precision and seriousness with which Twilight and Spike were approaching the experiment suddenly had her feel a twinge of nervousness. "I love you," she said, apropos of nothing.
Twilight cocked her head, but smiled. "I love you too. See you in a minute."
With a final nod, Rarity positioned her head. Twilight lowered the helmet.
The brim almost completely covered her eyes, darkening her vision. The metal slid smoothly over her horn. She could feel the buzz and thrum of magic rushing through the valleys and ridges of keratin as runes activated with a faint shimmering noise.
Distantly she felt Spike wrapping a cuff around her foreleg and pressing leads to her chest and flanks. Monitoring equipment?
The magic was intensifying, turning from a trickle, to a stream, then a river, but with purpose and clarity, just barely out of tune, like a song played on an old piano.
Rarity closed her eyes, focused on the notes, and then—
"Alright, she's under," Spike said as Rarity's shoulders slumped slightly. Her breathing became deep and regular. "Vitals look normal… Field is stable."
Twilight sucked in a breath and forced herself to hold it for a second, then exhaled slowly and purposefully. Her heart was racing with adrenaline. "Alright. Continue monitoring."
Why was she so nervous?
Maybe it was the different intensity of the subliminal waves emanating from the helmet. She hadn't been blowing smoke; Rarity's magic was exponentially finer and better controlled in essence than Twilight's own vast power stores, and it knitted and melded with the nebulous cloud of computational magic in fascinatingly precise ways.
Frighteningly precise, she corrected to herself as she examined the raw readouts and probed the field's incomprehensibly complex pattern of waves and particles, and she thought back on the start of the experiment.
She didn't know quite how she'd done it. A single magical particle, refined and compressed with just the right tuning, had suddenly vibrated and formed a stable state instead of dissipating into the ether. Magical vibrations sent into the particle caused it to respond with different but predictable vibrations.
Excited, she'd refined another particle and added it to the first. The interactions changed but remained consistent. She added another, and another. She'd doubled the size of the particle field, then doubled it again and again, then duplicated it again in overlapping layers. Each time the cloud grew fractionally larger, the amount of cross-layer interactions grew exponentially. She could send a complex signal into one area of the field, and get increasingly complex and consistent signals back out.
One day she'd managed to compress the field without breaking any of the connections. It could fit on the head of a pin instead of a room. The magic within had intensified. That same day, she'd sent a precise vibration into the field, and the unthinkable happened.
The compressed field had replicated itself.
Within a week, with some guidance, the magical construct had become self-sustaining, generating new stable subfields and reabsorbing old destabilized ones into the matrix. The system remained in relative equilibrium, never growing larger than the lab space, but rather feeding back into itself, generating new layers and shells of magic, becoming almost a living, breathing thing.
Even with her finest instruments, Twilight couldn't measure it at any more than a gross superficial level anymore.
But now, as Rarity sat peacefully in a trance under the helm filled with nearly-microscopic focusing runes, Twilight wondered if this might be the turning point for understanding. An exceptional pony who could not only intuit, but perhaps even directly perceive the inner workings of the construct.
"How's she doing?" Twilight asked, shaking herself out of the reverie.
"Excellent," Spike responded, poring over a series of blinking lights. A mechanical quill glided smoothly across a rolling scroll in fine patterns. "See? Primary waves are congruent, secondaries and tertiaries are correlated within parameters."
Glancing at the patterns, Twilight's brow furrowed. "Almost too excellent," she muttered, grabbing a quill in her magic and circling a series of arcs. "Look at that congruency. The margins are ten times closer than usual and the eccentricities are almost nonexist."
Spike shrugged. "You said her magic is a lot finer than yours."
"Maybe." She turned back to the field and peered at at a spot where the apparatus focused a cone of Rarity's magic into an infinitely small point. "Look at that."
Spike squinted and grabbed a stool. Walking into the field, he set it down and clambered up, then held a gem up to the floating spot and blew a tiny burst of dragonfire across it. The gem pulsed in a complex pattern with inner light.
When he moved the gem away, the pulsing continued.
"Look at that," he said, a note of awe creeping into his voice. "Measurable but stable."
Twilight's heart fluttered and her breath caught in her throat. This was huge. "Measure again and note down the deviation across boundaries."
Spike started scribbling furiously on a scroll, moving to various points in the field and infusing different gems with dragonfire. The glow of magic pulsed over his scales, the waves of the ethereal field floating through him completely unperturbed. Twilight grabbed her own notes and started writing as well, theoretical half-concepts and suppositions, with marginal notes as she sent probing pulses of magic from her horn into the cloud.
It wasn't until she moved on to a second scroll that her brain tinged with a warning bell. "Spike?"
"Hm?" His voice was distant and distracted.
"What was my longest session?"
"Uhhh…" Spike shook himself out of the focus he'd been in. "A little under three minutes. Why?"
"How long has Rarity been under?"
Spike's brow furrowed. He jumped off the stool and trotted out of the magical field to grab a small stopwatch. His eyes widened and he gulped. "Twelve minutes."
A vise clamped around Twilight's chest. Too long.
Wordlessly they both rushed to the chair. Rarity's breathing was still deep, her eyes closed, muscles relaxed. Spike pored over the readouts. "She looks stable, I can't see any problems…"
"Rarity?" Twilight gently shook her shoulders. "Rarity, wake up."
Nothing.
Twilight forced herself to take a breath. "Okay, did you ever do anything to bring me out?"
"Nothing." Spike shook his head, rechecking the measuring equipment. "Her patterns look just like yours, only deeper."
They both stood in silence for a moment. The only noise was the sound of the mechanical quill scratching over paper.
"I'm gonna try bringing her out," Twilight said. She reached out with her magic and gently pulled on the helm, raising it slightly.
An alarm bell sounded from the monitoring machine. Spike jumped for the readout.
Simultaneously, Rarity's forelegs stiffened and pushed against the chair. She cried out. A pulse of magic emanated from her horn, and the helm slammed back down.
Twilight slipped backward and fell on her haunches as she lost her grip. "What in Tartarus?" She stood back up, ready to try again.
"Don't!" Spike yelled. He waved the paper. "Look!"
With monumental effort, Twilight forced herself to pause. She looked at the readout.
At the moment she'd tried to pull off the helm, every single one of Rarity's vital signs had skyrocketed into the red zones. Not by much, and not for more than a moment before everything stabilized, but it was enough.
"Oh no," Twilight whispered, as the vise seemed to tighten on her chest. "Oh no."