"Why would they build a drop like this?" Rainbow Dash muttered. "That's what I wanna know."
"Beats the heck out of me, Sparky," Lancie said with a shrug. Together, the two watched as several craggy lengths of rock wall shifted past them. Rainbow's descent was a slow one, and the vertical tunnel glistened all around them. "Maybe the engineers who dug the tunnel were in this place for so long that they had to carve themselves a poop chute."
Rainbow's muzzle scrunched. "You're not making this any easier."
"Well, sorry, my little pony," he uttered with yet another shrug. "Nopony died and made me the king of mysterious mountain holes."
"Just as well," Rainbow muttered, peering straight down as she drifted earthward, slowly, wing-tips fluttering. "I wouldn't have you spelunking ahead of me to scout." She glanced at the walls drifting past them. "Funny. There's something different about the inside of the cave here."
"Uh huh..."
Rainbow Dash grazed her hoof against the pearlescent stone. "Everything here is so... so polished and pale. Almost as if it was burned away by something... like... an acid."
"Uh huh... ... ..."
"Dude, Lancie, give a mare a hand here!" Rainbow exclaimed.
"What do you want from me?!"
"Well, for one, are you familiar with this kind of rock formation?"
"Eh. I've seen it all before," he said with a yawn.
"Yeah? Like where?"
"Back in the days before Celestia and Luna," he uttered, breathing evenly again. "A lot of nasty things walked this earth way back when. Things that make the monsters of present day look like slobbering puppies." He grinned. "I found them all quite pleasant, company, actually."
"Yeah, well, what's pleasant for you may not be pleasant for me," Rainbow muttered.
"Don't worry, Sparky," Lancie said with a wave of the talon. "So long as the cave's surface doesn't get filled with a bunch of porous holes, we should be A-Okay—"
Right as he said that, the ruby light from Rainbow's stone caught countless round impressions forming like reverse goosebumps along the walls of the tunnel. Rainbow grimaced, looking in every direction as she was surrounded by what resembled the surface of a golf ball magnified a hundred times. The stone had even become ghostly pale, just like the item in question. There was a rusty smell about the place, and—if Rainbow Dash tilted her ears just right—she could have sworn she heard a distant hissing, sizzling sound.
"... ... ...huh." Lancie blinked. "Well, then, I wouldn't fault you for flying back the way we came."
"Pffft. And get lost back in that endless cavern up above?" Rainbow nevertheless looked straight up. Darkness clouded the air above her, and there was no making out the windy chasm from which they descended. "I wanna explore down here. At least a little bit more. Something tells me that this place was burrowed later on... maybe as a detour for faster, safer passage."
"Sure, why not."
Rainbow frowned heavily. "Unless there's something you wish to tell me, ya little melon fudge!"
"What's to tell?!" Lancie cackled. "I'm doing the same spelunking mystery boogie as you, Sparky! All of this stuff was sculpted long... long after I last donned a party hat on this mortal plane."
"Could you at least tell me what kind of a phenomenon would have—y'know—made this sort of a tunnel possible?"
"I could tell you several!" Lancie grinned devilishly. "Which would you like to hear about? The creepy crawly type? Or the creepier crawlier?"
"Unnnnngh..."
"It really isn't too late to double back, y'know."
"No can do," Rainbow Dash. "Apple Bloom—"
"Apple Bloom Apple Bloom Apple Bloom..." Lancie rolled his eyes. "Y'know, before this silly conundrum flounced itself your way, I hadn't heard a single peep of that name! Why can't we be risking our necks for a foal who was more prevalent in your goofy life? Like that scrappy orange one?"
"You leave Scootaloo out of this."
"Hah! With a name like that, you'd think she deserve to have it etched in a tombstone sooner!"
"Lancie, for the last time—" Rainbow Dash's hooves made contact with the floor of the passage, and she instantly regretted it. Sticky, fibrous material stuck to her fetlocks. She grimaced, flapping her wings and lifting up until the gelatinous substance snapped free. "Eeeeugh... mega gross. Just what in the heck was that?"
"I'm tellin' ya, girl. Poop chute."
"That's not how poop works," Rainbow grumbled. "Besides, I think we're the only ones who've been down here for years." She peered about, shining her light on more porous rock—exposing a jagged tunnel that zig-zagged due west in an uneven pattern. She gulped. "The only civilized ones."
"Just ask yourself one question, Sparky," Lancie murmured. "Is Apple Bloom worth all of this?"
Rainbow Dash took a deep breath.
"Well?"
"I've never backed down before." She flew forward, wings outstretched as she threw herself into an even glide. "I'm not about to now."
"You realize how foolhardy that sounds?"
"I'm motherbucking loyalty incarnate," Rainbow snarled. "Let the world toss its fools at me."
"Spoken like a true corpse."
"Good. Then start recording."