A series of pressurized doors rotated open in opposite directions like giant cogwheels. Once the path was clear, a stallion in uniform gave a signal, and the passengers on board the undertrolley trotted out in single file. They entered a wide hall with a curved, domed ceiling.
As Rainbow Dash entered Shoggoth, she tilted her head up... up... and up. She gawked at several curved platforms looming above her—one level atop another—and all occupying barely a fraction of the enormous space of the underwater dome. All around—in a nearly unobstructed panoramic view—Rainbow Dash could see out into the watery plains of the ocean's floor. The seaponies' dwelling lit up to the west and the east with shimmering patterns of bioluminescence. Meanwhile, to the north and south, spires and brightly-lit domes lingered in close proximity—just a brisk swim away.
The station's interior was a loud, bustling place—with no end of chatter, noise, or bedlam of mixed conversation. Rainbow Dash saw earth ponies, unicorns, and pegasi in countless different styles of customary attire—all chatting, bartering, and commiserating in various collective droves. Their bodies—and the structure as a whole—was lit up by streams of gold and amber light that emanated from the outer ring of the dome, giving the already copper color of the riveted surfaces a red-orange glimmer, like fire.
Most curious, however, were several pools of crystal-clear water, separated by tall vertical support columns built out of... what appeared to Rainbow Dash to be see-through, translucent glass. All of the surface-dwelling equines kept their distance from these watery canals, and the columns stretched up and ran through strategically placed holes in the upper platforms overhead.
It was around this point of constant observation that Rainbow Dash became aware of an accute, persistent groaning sound. Every now and then, the ambiant bass noise would ripple and clash, resembling cymbals that slammed in the distance, only to be answered by melodic chimes and muffled bells before becoming obscure once again.
“What... what in the hay is that?” Rainbow muttered.
“Annoying bullshit,” Echo grumbled from Bard's backside. “That's what.”
“When you have millions of tons of ocean water rolling over a metal eggshell, there's bound to be some auditory effects,” Theanim said with a smile. “As for the more pleasant moments of tonal quality, you can thank the sea ponies for that.”
“But... but I thought you said we couldn't hear them,” Rainbow said.
“Ah. It's more like we're hearing... the dome hear them,” Theanim explained. “A structure this big simply magnifies their song all around us. Let us not forget that the Muddredger city belongs to them as much as it does to the Muddredgers themselves.”
“This is place is... just so cool,” Rainbow remarked. With flapping wings, she lifted herself up for a better look. “Way cooler than I thought—”
A metal talon suddenly yanked her down by her tail.
Rainbow grunted, then frowned at Wildcard. “Dude! What gives—”
“Don't ya know anythang?” Bard exclaimed, glancing off at the distant guards on patrol. “Flyin' ain't allowed in these crazy underwater cities.”
“Yeah, why not?”
“Dun ask me.” Bard shrugged. “Them's the rules!”
“Well, it's a lame bunch of rules,” Rainbow muttered. “But whatever.” She looked to her right. The group had wandered towards the edge of the domed structure, and Rainbow Dash found herself staring at a cluster of rocks covered in vibrant coral and billowing sea anemones. “Whoah...” She murmured, lips pursing in awe. “Just how thick is this glass?” She reached he wing out, feathers stretching. “It... it looks so crystal clear—”
Her feathertips dipped into cool, wet water.
“Gaaaah!” Rainbow hopped back, eyes wide as she huddled behind Bard. “There is n-no glass!”
“Hah hah hah hah!” Bard guffawed, slapping a knee. “Ohhhh... took her longer than I thought to notice!”
Wildcard smirked.
“Dude!” Rainbow looked over Bard's shoulder, gulping. She watched as circular ripples oozed outward from where she had touched the curved liquid barrier. “What g-gives?!”
“You really must be from another flippin' world if you ain't never heard of Siren water charmin'!” Bard said.
“Actually, Mister Bard, the correct term is 'aquakinetic engineering,'” Theanim stated. “It's a form of underwater sorcery that's existed for thousands of generations.”
“Pffft... my grandpa always called it like it is!” Bard tossed his mane back. “Siren water charmin'!”
“But... like...” Rainbow grimaced, gazing up at the see-through parts of the dome overhead with a new sense of dread. “...h-how can ponies... sea ponies actually make water stop for no reason?!”
“Pfft! Hell, it ain't for no reason!” Bard smirked. “Haven't you ever thought how plum weird it'd be for non-pegasi to meet a pony with wings who could control the weather?”
“Huh...” Rainbow blinked, nodding. “That's one way of putting it... wait.” She turned around, gazing once more at the pools of water in the center of the platform—or more spacifically at the clear vertical columns erected alongside them. Upon a secondary examination, she could spot rippling texture to the cylindrical structures. “Those... are all water too.”
“Damn skippy,” Bard said. “Though, I never done seen anythang quite this elaborate. This is about as deep into Siren territory the Desperadoes have ever done mosey'd, ya feel me?”
“Did you seriously expect glass and ironworks to be this city's only barrier against the elements?” Theanim mused. “Shoggoth would have perished decades after its initial construction if that was the case.”
“Yeah, well, live and learn.” Rainbow glanced at the stallion. “I was born in a giant cloud city built out of smaller clouds that floated around wherever it pleased.”
Theanim chuckled. “I'm glad that you're having such a learning experience, Miss Dash, but please—don't use hyperbole to try to best it.”
“No, for real, though—”
With glinting goggles, Wildcard pointed straight up.
“Hmmm?” Theanim and the others turned to look. “Oh, what splendid timing!”
“Huh?” Rainbow looked. Her eyes reflected several amphibious figures swimming rapidly towards the edge of the dome. As they came closer and closer—not even remotely slowing their stride—she could make out colorful eyes and even more colorful smiles. Already, a group of conversing merchants and travellers spread apart, forming a clear line across the bottom platform of the station.
Within seconds—SPLASSSH!—a dozen sea ponies carrying thick bags shot through the water barrier. They dove through the air like dolphins, dribbling a trail of moisture across the clear platform beneath them. Before Rainbow could blink, they had all plunged into the many-many pools littering the floor. Swift as lightning, some of them went under, reemerging in the vertical columns of enchanted liquid. Rainbow watched as various equines darted up and down the watery tubes, swiftly delivering packages and materials to multiple levels within the dome. By the time it was all over, the merchants shifted back into place, reoccupying the momentary splash zones and casually resuming business as usual.
“Huh...” Rainbow blinked. “Okay... this place totally rocks the socks off Cloudsdale.”
“Are we done with the damn sight-seeing yet?” Echo moaned.
“Reckon we'd better get situation,” Bard said, shuffling the weight of the Sarosian on his back. “Where to, Doc?”
“We'll want to proceed to the next structure north of here,” Theanim explained, motioning the group along. “Allow me to show the way.”