Penumbra was gone for hours. Iron Quill had other tasks to do in the meantime—being the Lord Commander of the army wasn’t a position ponies aspired to because it was easy.
He reviewed proposed settlement maps for the caverns, in particular one that Silver Needle had drawn up just the day before.
“We might not even need a magical solution to this,” she said, gesturing at her illustration. “Ponies have been living in frozen environments before, and we’ve always managed.”
“Ponies in the Empire used the Crystal Heart,” Quill said, inspecting her drawings.
They depicted a slice of the huge cavern, no longer structured into military camps but instead into much smaller dormitories, with whole companies sharing each one. Instead of parade grounds and open storage, each one used buildings she’d drawn on another sheet, packed as close to each other as the shields in a defensive formation.
“In the city, maybe. But everywhere else, ponies improvised.”
Silver wasn’t the only pony here—though none of the scientific ponies were present, representatives from his new “company” of non-combatants were here, along with the leaders of the two larger labor organizations from outside the camp. The ones that had once been responsible for supplying their army, and building the permanent fortifications they needed as they advanced into Equestria.
The builder was an older earth pony stallion named Mortar, who scowled down at the blueprints with disdain. “You don’t want us to build this. It’s wasteful, just look.” He held it up towards Quill. “Lord Commander, look at these walls. Two inches, then a cavity, then three more. What a stupid waste of cement.”
“I didn’t think we had cement anymore, Mortar,” said his rival—the only griffin in the entire army, so far as Iron Quill knew. If the old bird knew who he was, she hadn’t ever indicated as much. The burned feathers down her left side wouldn’t be making it any easier for him to sleep tonight. “You can’t build it anyway. But we can, Lord Commander. We’ve already discovered a useful mineral. Our masonry is limited only by our supply of water.”
And our supply of water is tied back to our fading heat. It’s all connected. Nightmare Moon had not lied on the first day, when she said there were a thousand ways they could die. There were probably more than that, all connected and no less terrifying when it finally killed them.
“We’re working on a way to address the water problem,” he said. “Or more accurately, the heat problem. We have a limitless supply of ice, but the oil to melt it is… dwindling rapidly.”
Silver Needle tapped her quill against the table in her magic. “E-excuse me…” she said, voice timid. “It’s, uh… it’s not silly, Lord Commander. Putting everypony together like this, it puts all their heat together too. The internal walls are thin, only the ones built around it use this design.”
“But why?” Mortar asked gently. “Empty space doesn’t keep ponies warm, stone does. Other things would work better—wool maybe, or even straw. But I think we need every bite of it we can get.”
Iron Quill nodded. “The supply of straw is already being mixed with our rations. I suppose there’s no reason we couldn’t store it inside a building.”
“We don’t need to,” Silver said. “Lord Commander, just having the building hollow will be enough. The fort in Defiance is built this way, as well as Castle Icefalls. Those engineers knew what they were doing, even if we don’t. I grew up in Defiance, and it was toasty warm even during the worst blizzards.”
“Very well. Mortar, have your stallions begin making bricks. Store them here, in preparation for assembling the first of these structures.”
He turned. “Jacinda, I want you to pick a place outside of camp, and build two rooms for me, each five foot square. One with walls five inches thick, and another using this method. We will put this design to the test before we commit the resources of the entire army. Send for me when you have my results.”
Both nodded, accepted their payment, and left. Though the gold isn’t unlimited either. How long until ponies start realizing there’s nothing to spend it on?
“There’s really no need,” Silver said, once the contractors were both gone. “I’ve seen it before. This isn’t gambling on something new, it’s well established.”
He nodded. “I’m sorry, Silver. But sometimes I need to waste a little in order to head off challenges before they come. This army will resist your plan—they enjoy their independence. The companies will be furious when we force them to live closer. I must be able to demonstrate that every aspect of the plan is proven.”
She nodded weakly to him. “I… understand, Commander. I’ll continue to learn from you.”
“And pray you never wear this diadem,” he added, as she left. “It isn’t the army we really have to be afraid of, it’s the one who commands them.”
Silver Needle pulled her hood up, shivering as she left the tent behind and returned to the cavern.
The glowstone overhead suddenly dimmed, and the furniture shook. Silver turned to glance inside, and he waved her off. There was nothing for her to do about what was coming.
A second later, and Penumbra emerged from the shadows, bringing a cloud of dust with her that puffed up into the air and scattered all over everything. She brushed it away from her face with one leg, shaking herself out and settling the saddlebag down on the table with a heavy thump. “Why can’t you just ask… something reasonable next time?”
“You’re back!” He jumped to his hooves, hurrying over and scanning the bat for any harm. Even knowing that she wasn’t alive—not really alive, anyway—there was no way not to feel worried. She’d just done something that would’ve killed a regular pony in several different ways, and returned to speak of it. “Are you alright?”
“Fine,” she said. “Just dirty, and maybe a little annoyed. Everypony else was walking around out there, and I thought I got off easy. Stay inside, follow around a pony. Maybe somepony tries to knife him, maybe I have to cut a few throats.” She coughed, expelling a lungful of dust into the air. Not so much exhaled, more like she’d just dumped it from somewhere. “Ugh. That’s awful.”
“You sure you’re alright?” Frost was forming on her armor, turning the polished metal cloudy white. It spread over more than that, covering her coat and mane and her face with a dusty white layer. “You look, uh… cold?”
“Don’t feel cold,” she muttered, brushing away at the ice from her eyes. “Annoying, though. Fairly sure my eyes froze open or something.”
He shuddered, looking away. Too bad I can’t go back and help you make better choices. But that didn’t work out very well for Nightmare Moon. “Do you need a healer?”
“Nothing to heal,” she answered, hacking out another mouthful of dust onto his table. “Just give me a minute to warm up. Well… maybe more than a minute in this wasteland.” She nodded towards the saddlebags. “Found your thing, though.”
Quill leaned forward, flicking the bag open and looking inside.
There was an uneven lump of metal, its shape strangely melted and swept back along one side. It was dull and lumpy, with vaguely circular patterns where it hadn’t been hammered or cut.
But how it looked was less important than the warmth he felt radiating from it.
“Broke that off… something bigger,” Penumbra said, gesturing to the other side, which was almost perfectly flat. “Bottom of a shallow hole, I don’t know how far from here.”
“Wait.” He spread his wings to make her stop, then glanced over his shoulder. “Chain Mail, are you there?”
He poked into the tent. Like most ponies, he now wore full winter gear, a thick cloak over his body along with boots and a hat. “Of course, sir,” he said, breath billowing out in front of him.
“Bring Shade and Cozen, right away.”
They didn’t take long to arrive—Sylvan arrived almost instantly, and Cozen slunk in three or so minutes later, wiping the frost from her face as she clambered in the tent. “Oh, you’re… where’s the campfire?”
“It’s not that much warmer, don’t exaggerate.” Even so, Sylvan sat beside the rock, holding one hoof above it.
“And for the record, it doesn’t burn,” Penumbra said. She’d returned her wrappings by the time these other ponies arrived, though they were still covered in surface dust. “It’s warm, that’s all. Like leaving your sword in the sun all day.”
“What was it like?” Cozen asked, hurrying forward and touching the rock cautiously with one hoof. She didn’t catch on fire either—nothing particularly happened, in fact.
“Was there anything better?” Sylvan asked, not giving her time to speak. “I was looking for something obviously transfigured. This just looks like a semi-pure metal lump.”
Quill just found a chair and watched. He could barely even tell that the tent was warmer, assuming it even was. But he’d felt the metal himself, and it was certainly real.
“I didn’t find anything warmer,” Penumbra said. “I couldn’t tell they were warm without touching them, through my uniform. I went to as many craters as I could. All I can tell you is the more metaly-looking ones like this were the hottest. There were lots that seemed more… rocky? Those weren’t as warm. But still warmer than the sand.”
“The rock didn’t finish elemental transmutation,” Sylvan muttered, finally taking his hoof away and hurrying across the room to his cart. He started shuffling through it.
“No,” Cozen said. “I think we were wrong about transfiguration. The impact must not have been strong enough.” She looked up, meeting Quill’s eyes. “Did you feel this when it first arrived, Quill?”
“Lord Commander,” he corrected, without much anger. “Yes, as soon as she took it out. It could probably warm one soldier’s bunk quite nice, but not much more. It isn’t the solution we were looking for, is it?”
“It’s not that.” Cozen gestured. “Could you touch it again? I want you to tell me if it doesn’t seem as warm as the first time.”
Sylvan hurried past them with a file and a little box. Before Quill could protest, the earth pony scraped away at the rough edges of the stone, sending sparks up into the air. “Ah hah!” he said. “I’m nearly certain, just give me another moment…” And he dashed back to the cart, digging through little jars and vials.
Quill walked past him, eyeing the earth pony skeptically in case he was going to charge across the room again and run into him. When he didn’t, he touched the stone with the side of his leg. Not the frog, that was just too sensitive.
As before, the rock felt pleasantly warm to the touch. “I, uh… I suppose it might be a tiny bit cooler. It isn’t as uncomfortable this time.”
“I don’t think this is alchemical at all,” Cozen muttered, slumping into one of the cushions. “Another dead end, Sylvan.”
“How?” He looked up, holding up a little clear vial. He added the metal filings, and it tinged slightly green. “Because it’s just iron?”
“Well yes, but not just that.” She turned, addressing Quill. “There’s no conversion here, Lord Commander. This is just iron. It’s warm because the craters your… she found it in were in the sun. They must have… retained some of their heat, somehow. It really is like leaving a sword in the sun. I don’t see how this could help us during weeks of night.”
“It’s just iron?” Penumbra stomped past them, removing her armored gauntlet and reaching out for the metal. The other two turned away, shielding their eyes and shivering. But there was nothing under there but pony.
“Oh please.” Penumbra pulled her leg back, sticking the armor back on. “You know that’s just a story, right? You won’t have a life of nightmares if you see me.”
“Really?” Sylvan relaxed, settling his vial on the table. “I thought that information was reliable.”
“Those stories are to protect our identity from outsiders who can’t be trusted,” Penumbra said. “But there aren’t many outsiders here on the moon, are there? Ponies saw my face all the time when I was working, and they didn’t have nightmares.”
“There’s so little real magic out there,” Cozen agreed. “Even when we want it, there’s nothing to be found.”
“Usually we just cut their throats,” Penumbra went on, her tone so casual Quill didn’t believe for a second she wasn’t doing it intentionally. “So they couldn’t reveal who we were.”
Sylvan froze, clutching at his throat with one leg.
“You saw her leg,” Quill pointed out. “Don’t frighten the ponies I need to be clever.”
“It sounds like they were saying I took that trip for nothing,” she said, glowering. “You know how hard it is to get dust out of your mane when we don’t have the water for bathing anymore? Very.”
“I’ll go myself next time,” Cozen muttered. “Look, I’m not happy about it either. But the truth isn’t going to change just because we don’t like it. If it’s not the solution, we need to find what is. Before we freeze.”
“Seems like you have it already.” Penumbra sat down beside Quill at the table, something he couldn’t ever remember her doing. She showed no sign of returning to the shadows. Maybe she wanted to get dust all over them.
Sylvan turned, walking away from them to the construction sketches on the far side of the room. He didn’t seem to be paying attention.
“We don’t,” Cozen snapped, glowering. “We’ve explored every option, believe me. There are spells that make heat, but they take concentration from the caster, and tremendous energy. I don’t think anypony besides the princess herself could do more than five minutes of the spell before it collapsed.”
“Not that,” Penumbra said. “I don’t know anything about unicorn magic. What makes you think I was talking about that?”
Cozen glared. “Well, there’s no alchemical way to just make heat either, not with what we have. Many reactions produce fire in direct or indirect ways, but we don’t have them in quantity. We would need to mine an endless supply.”
“Not that either,” Penumbra said. “I know even less about alchemy than I do about unicorn magic. At least I sometimes have to fight unicorns, and I have to know how they might try to kill me. But alchemy—that’s for scholars in high towers. Totally safe.”
“There’s conversion,” Cozen went on. “And we’re already working on that. It might help, I don’t know how much. Lord Commander, you don’t need to have her do this. Just because I forgot your—”
“I didn’t tell her to do anything,” Quill interjected. “But I do find it useful to hear what you’ve tried and what failed. What do you mean, Penumbra?”
She took another moment before she finally answered. At least the frost seemed to be gone from her coat, melting away in the more comfortable temperatures of the tent. They weren’t all freezing to death quite yet. “The thing you’re doing to melt water,” she went on. “The… metal. You heat it up with tiny bits of lightning, it gets warm, ice melts. Why not just stand up one of those facing the cave, really huge, and just… blast it? So long as nopony touches it, they shouldn’t get fried, right?”
“Because…” Cozen stopped. “Why don’t we do that?”
“Because making something that large would take ages, and by the time we finished forging it the sun would be out already. And because we only have so many bolts. Those are how we’re making air, so… when they run out, we’ll be double-dead.”
“There’s a better way!” Sylvan hurried over, dragging one of Silver Needle’s preliminary sketches. It showed the camp all packed in near the top of the cave, where it was still long and thin instead of the expansive dome they were in now.
Other than the basic wall design and close quarters everypony would be living in, the design had been so covered in Sylvan’s sketches that it barely even resembled the same plan anymore.
On the lunar surface above, shown only as a single line in the drawing, a vast flat sheet was now visible, made of metal with a few conical spikes running down—all the way down, into the cavern itself.
“This is…” Quill frowned, studying the drawing. What it had to do with the things they’d learned, he honestly had no idea. Metal getting warm in the sun of the lunar surface, sure, but…
“It’s all back to this rock,” Sylvan said, tapping the warm metal lump with one hoof. “Why this is still warm… it’s all connected!”
“Okay.” Quill sat back in his cushion. The sketch didn’t just have metal running straight into the center of each camp, there was some strange interlocking mechanism. But he ignored those for now in favor of the more obvious problem. “The hollow moon is what’s holding our air in, Sylvan. You’ve just made holes in the roof.”
“Yes yes,.” Sylvan waved a dismissive hoof. “There are clearly ways to stop it from leaking with rock and ice, or it wouldn’t stay here in the first place. That’s the least important part of all this.”
Cozen leaned across the table, inspecting his design. “You should stick to alchemy, Sylvan. I’ve built enough magic tricks in my time to know it won’t work. Too many moving parts. We need something simpler.”
“This is cute and all.” Penumbra glared between them. Particularly at Cozen, who was hurrying over to the drawings and looking through more of them. She found an early version of the structures in the current dome, and stole Sylvan’s quill to mark it up herself. “But you didn’t actually say how this stupid plan is supposed to work. You’re already changing it, without even…” She rose from the table, turning away. “Whatever, Quill, you sort this. We’re all still alive so far, I assume you know how to herd these bats.” She stepped back, vanishing into the gloom.
And of course, she wasn’t wrong. “Please explain, Sylvan. We went to the surface to find fire-stone, and we failed. So what’s the point of… all that?”
“Heat,” he said. “Well, heat and water. It’s all connected. We play to our strengths. What do we have in endless supply? Ice and stone. And the surface has as much metal as we could ever need. I’ve been…” He trailed off. “I’ve been part of this army long enough to see what a determined Alicorn can accomplish when she really wants to. Her and the Voidseekers could fly far, bring back tons of metal like this, then she could use her magic to melt and shape it into the largest possible sheet.”
He nodded towards the lump. “It’s warming in the sun. The more metal can see the sun, the more it heats. So it’s widest at the top, then narrowing and thickening to bring the heat below. Down here, they’ll be submerged in water, with more thin metal on the outside facing into everywhere ponies live. We can use screw-pumps to lift it out and into smaller tubes. If it gets too hot, we just shut them off, and close the water off with—”
“Too complicated,” Cozen said again. “Good premise, way too hard to build.”
She turned her own sketch over. “See these changes, Lord Commander?”
It looked much the same, except that instead of a dozen little cones pointing down, there was just one massive section, leading into a large reservoir filled with water. “Instead of one cone and one tank and one pump for each company, we have just one of each in the center of our single building—or the cave, whichever. When it’s warm or we’re thirsty, we add ice. When night comes, we open a chute here, and the hottest water can flow down through more metal in each building around it. The water flows passively back to a collection tank at the bottom, and we have a single pump there to lift it back into the top.”
“I do like your design,” Sylvan muttered. “The difficulty is getting the single large chunk of metal. The entire plan revolves around the princess’s cooperation. Nothing will work without her.”
“Actually it seems to rely on… thousands of bits of construction, a total reorganization of our camps, and some still fairly-complex mechanisms.”
“Don’t worry about the last one,” Cozen said. “We already have some skilled tinkerers in the new camp. They can build the pump.”
“I’ll have to take the plan to the princess,” Quill said. “Only she can decide if she is willing to scour the moon searching for metal, and flatten it in this way. But supposing she supports the plan, we still have to survive ten days before the sun returns. And… we’ll still have one opening to the outside, won’t we? This metal spike drives right through the ceiling above us.”
“Melt it,” Sylvan said. “Melted sand is glass, and glass holds air. Melting enough for a vessel for all of us is beyond our power. But melting a seal around a single object is certainly within reach of an Alicorn. Considering everything else she’s done…”
“It depends on her.” Quill rose suddenly, lifting a fresh parchment scroll and settling it in front of them. “Draw a clean version of the second plan. I have another plan to keep the camp alive in the meantime. These ponies are going to bucking follow my orders this time.” Even as he strode from the tent, he unslung the Lord Commander’s horn from his shoulder, and gave three short blasts. The cave rumbled with it, and his summons was given.
They came. Not galloping in with their honor guard within minutes at most, as had once been the case for the best-honored of all the army’s Lord Commanders. But they still came, meeting him outside the tent. All had fitting uniforms now, cleaned of the bloodstains and tears that had been common on the first day.
Or maybe that was just the thick coats, covering up everything but their eyes in some cases. A few captains had forgone armor completely for bundles of winter marching gear.
“Three blasts,” Uttermost said, as soon as they were all there. “Are we marching back to Equestria, at long last?”
“My stallions are at the breaking point,” another captain said. “We better be returning soon. I don’t know that the army will survive much longer.”
Iron Quill shook his head once. He watched for the signs of disloyalty, or the arguments about to begin, but none came. He saw a little fear from some of them, in fact, eyes that glanced to his belt and the sword hanging there. Iron Quill had taken the most powerful warrior in the army and burned him alive before their eyes.
If fear is what it takes to get them to follow me, then I’m okay with that. So long as their ponies survive. “We march, but we cannot yet leave the moon. Only the princess can do that, and she devotes all her power to it every moment.” She also doesn’t think she’ll be able to do it for years and that we’re all doomed.
“Then where are we marching to?” Uttermost asked.
“The tunnel entrance,” Quill said. “You have two hours to marshal your troops. Tell them to leave all supplies of war behind—no weapons of any kind. They are to carry camp bunks, any blankets or freezing weather clothing they own, and their personal effects.”
“And we’re marching to…” said White Tallow. He’d been first to side with Permafrost, which meant he was now among the most fearful of these ponies. But apparently willing enough to question him.
“The tunnel,” he said. “We will march past my camp, to where the camp followers have begun establishing their… whatever they’re building.”
“I assume you’ll be leaving your soldiers here,” Tallow muttered. “With all that’s left of our oil and wood to burn. While the rest of us freeze with the scraps.”
“No.” He cleared his throat, glaring harshly. “And if you ever suggest I’m disloyal to this army again…” He didn’t follow through on the threat, staring intently at White Tallow until his ears finally flattened and he looked away. Quill went on. “My scholars have determined a solution, but it will not help us until the sun returns. We must survive until then with what we have. Any of you who have served in the far north should recognize what I suggest.”
“Smaller tent is a warmer tent,” somepony said.
“Right. We will make a tent warm enough to survive, while remaining close enough to briefly allow the cold in and keep exchanging our air with what is produced in my camp. Many of my ‘soldiers’ will be forced to continue their work so that you can keep breathing.”
There might’ve been objections before, either in the form of fierce arguments or silent agreement that hid a true intention not to act. He saw neither now. “I’ll be bringing all the oil we have left. Not the wood—my alchemist tells me we must conserve that. But the oil we will bring, and we will burn if necessary. If you do not follow my orders, all your stallions will freeze. Are we clear?”
He waited for their agreement, one at a time.
“Then go.” He lifted the horn, blowing three blasts again. “And remember—no weapons. If I find so much as a dagger on any of your stallions, I’ll order the Voidseeker to stick it in your gut.”
A lie of course, he still wouldn’t break the sacred protection captains were afforded. But as he stormed away, he caught one last glance of their faces.
They believed him.