Spike's intention for inviting Pinkie, once he actually had one... Well initially it had been to get her help in making things more comfortable for the Diamond Dogs. She could have brought support in addition to the protection and aid he'd already offered. Having been driven from their homes wasn't something he could entirely make better on his own, no matter what powers or skills he had gained along the way. While he knew Pinkie was no stranger to combat, he also figured she probably didn't want to join him in killing off a large infestation of insects.
Maybe if today's target had been any other group of insects that would have been true.
That is not how things turned out.
Snarly brought them through the tunnels and into the warren on the same increasingly-regular trail Spike had used before. Pinkie had given an array of ooh's and aah's at what they’d accomplished, with extra-emphatic approval for Spike's reinforcement and decorations. It warmed his heart, doubly so as the two of them exchanged nudges and giggles mid-walk.
Their tour ended with a final stop just outside of the throne room: King Rudy wasn't present, but a council-member Spike had met before was. Pinkie stayed by him and listened to the explanation of what they'd be dealing with today, since Spike hadn't even brought up his hypothetical plan yet.
And he never got a chance to do so. The moment that the councilor mentioned their problem was with Bermites? Pinkie Pie went ramrod straight and whipped her head around to stare. A real proper capital-S Stare, really. Her eyes were practically burning with blue fire and the tone of her voice was underlined with a vicious growl.
"Where are they?"
The relatively docile Dog was shocked and surprised by the force in this pony guest's voice, although he eventually stuttered out a reply.
"U-under the tunnel we used to reach this place. Long wide nests, we think."
Spike raised a claw to ask what was even going on but Pinkie's sudden continuation cut him off. She spoke rapidly and moved even faster, pacing the ground outside the throne room at full speed.
"Under the tunnel!? That's no good! We've gotta act fast if you care about going back home ever, because that place is all gonna collapse like a bad cake otherwise! The problem always starts from down below with these darn things."
When Pinkie saw Spike's surprise and confusion, she just giggled and pronk'd back over to him as if a switch had been flipped.
"Rock farm, remember? I've been dealing with those nasty lil' bugs for as long as I can remember! You should have seen my sisters last time we had a nest to burn out. Super duper scary... I guess I probably was too, but I was inside my own head at the time so I couldn't exactly tell."
That made sense, or as much sense as anything did adjacent to the concept of a rock farm.
"Right! I guess that would... threaten the... crops?"
"Oh for sure. Which would be bad enough on its own, but now there's all these dogs down here! Not that there's any chance of things going wrong: With both of us working on it, I bet we can take care of the problem in even less than half the time it'd take alone!"
That... was honestly a better plan than his original idea. Heck, the two plans weren't even mutually exclusive! They could both handle comfort and hospitality for the Dogs afterwards. Why skimp on resources in the front half? And given his past experiences with both Bruxis and Piercing, he had a feeling that watching Pinkie Pie fight against a foe she had history with could be... illuminating.
"Sounds like a plan: Out to the nests, clear the place at full force, come back here for pastries?"
Pinkie quirked an eyebrow and leaned towards him, trying her best to loom over him... Ignoring how their heights were a lot closer these days.
"I dunno if you're ready for my 'full force' solution to rock-biters, Spike."
"Hey, I eat rocks too!"
"Yeah but you're people! Person. Dragon? Cute. Whatever really: You know what I mean."
He leaned up across that last bit of distance in order to kiss her cheek in lieu of a reply. Then he thanked his perfected memory for safely storing the image of Pinkie Pie's blush in the shadows. With that taken care of he turned back to the somewhat rattled Diamond Dog nearby.
"I got a pretty good feeling for the layout over my last few visits, councilor: Want that we just take care of business? I don't think we'll need any guides or guards."
The foppish Dog still seemed a bit rattled by Pinkie's earlier display, or maybe unnerved by their displays of cross-species affection? Whatever, his loss.
"Y-yes that would be for the best! Thank you again for your hard work, er, both of you."
If Spike or Pinkie had been down here alone in this situation, maybe they'd have been held up for a few minutes with pleasantries. Disengaging from the conversation slowly and making sure there weren't any issues, that kind of thing. As it is, both of them exerted wordless pull on the other: If they put it into words, it might have been a bit like 'The Dogs here can handle their own affairs just fine, as long as we get out to the frontline.'
So that's exactly what they did.
- - - -
The wide and exceptionally carefully-carved tunnel would have surprised a lot of ponies: You'd usually think about an escape tunnel as something hastily-made and designed to be abandoned, or even the sort of thing you'd backfill to slow pursuit. But there were a couple of problems with that train of thought.
First, that logic works just fine... when you're moving a small group, one time. When you're moving your entire civilization in one amorphous exodus, with hope of returning the way you came one day? You take your time on safe and stable workmanship, even if you're trying to work fast within those constraints.
Secondly, that concept also only works if your pursuers aren't better tunnelers than you. Doubly bad was the fact that Bermites actively fed on loose rock, so trying to cave in the tunnels would only make the bugs happier and give them a direct trail to follow. Empty space was less appealing to them, smoothed and reinforced stone even less so.
So the Diamond Dogs had made their egress from their traditional homes slowly, with intention and clarity. The resulting tunnels were clean and smooth, with fractures and loose pieces carved away to avoid any rubble or scree. (Actually, was it still even scree underground? Whatever.)
Pinkie Pie whistled as the two of them walked down the path, her eyes darting from one segment to another with a kind of nostalgic joy.
"Yeah, it'd definitely be a shame to lose this tunnel: Once this all blows over I'll have to get Maud out here! She's more of a stand-alone rock girl, but if any Pie can appreciate a good burrow it's her."
"Maud of the infamous muffins from last year?"
"Yuppers! Oooh, maybe I could bring her out here for her birthday this year!"
Spike kept his nerves tamped down under sarcasm, which wasn't anything unusual. The nerves were, but they just boiled down to his mounting realization of how bad this situation could get.
"Assuming there's a ‘here’ to bring her out to by then."
Pinkie poked him in the shoulder and set him, not stumbling, but gently sproinging back and forth. She covered a giggle with her hoof: He knew she appreciated having a willing player for her gags.
"Don't be negative about it Spike: Nopony gets things done by planning to fail!"
"Yeah. I just... It was one thing when I was helping out the Dogs at first and thinking of this as a series of small problems. But now it's looking a lot bigger."
"Well Spike, you know what I like to do when a problem looks real big?"
He raised an eyebrow, wordlessly asking her to continue... What he got in return was a glimpse of that full-force Pinkie Pie they'd joked about, as she stalked down the tunnel with purpose in her steps and a truly manic grin on her muzzle.
"I like to break it down into pieces."
- - - -
Inspection Results:
It started dramatic and ended a little more subdued: Pinkie Pie's declaration was weighty and honestly kind of hot, but she (probably) meant it a lot more metaphorically. They took things slow and steady, starting from the obvious. A party was formed under the name 'Another First Kiss' and the two of them demarcated their halves of the enormous stone hall.
Spike used Dragon's Eye, Earthshaper, his affinities and Observe in order to scope out his share. Pinkie Pie had a life spent growing up on a rock farm coupled with all of her usual oddities in order to gather her own conclusions. After they stopped finding obvious signs of damage partway down the tunnel, they doubled back to where they started and shared information.
"I counted about thirteen rooms... No that sounds too formal. Chunks? Thirteen chunks on my half."
"So... chunks, huh?"
Pinkie Pie let that statement linger for a moment, looking slightly above and past his shoulder.
"But yeah I got about the same! Twelve-and-a-bit: I can hear the burrowing still going on at the end."
"Seems to be a large-scale work in progress, and they're probably clutching. Breeding? Whatever the term is there's a lot of them, and regularly-sized groups are staying in the finished... chunks."
"They're not going too high up and messing with the stability of the floor yet, and I can't find any spots where they broke through on my side either. Kinda weirdly organized, honestly!"
Spike pointed off to one corner, to the area where he'd found the most important detail. The rock wall there was just a hair thinner than the rest, and there was no equivalent on Pinkie's side of the hallway. Observe was a little bit cheating under the circumstances, but...
"Rather than breaking through into the tunnels, I think they just went straight under: There's a weak spot on the other side and I think it ties into some of the nests I cleared out on my past visits."
"Ew, that kinda does imply they're spreading out more. I guess whatever scared everything out of the old house musta been so scary they've got no plan of going back!"
"Makes as much sense as any alternative, yeah. So what's the plan?"
"I didn't think we had one! Momma Pie always used to say "Tis not ours to wonder why, only to do our duty", and I think this is one of the very few situations where it actually applies. I kinda just wanna go down there and take care of business toot sweet! Although I guess we're only gonna be baking and cooking afterwards so the sweet part isn't as relevant. And there won't be much music so the toot isn't very helpful either. Prench is a silly language is what I'm trying to say!"
Spike held his claw out to Pinkie Pie and pulled her close, cherishing the way her giggle effortlessly melded into her faux-surprised gasp. They were going to need stamina for the work ahead, so...
"Silly or not I think it's at least half right: Care to join me in a song?"
Cantus.