Finn had been sitting on an empty crate outside the tunnel entrance for forty minutes with his bag between his feet, rehearsing his opening line, when Lord Harold walked straight past him without stopping.
"Lord Harold—"
"With me, Finn."
He scrambled up, bag swinging, and fell into step two paces behind.
Harold looked like he'd been through the battle and hadn't stopped moving since. The Thresher King's armor was still on him — deep grey-green scales across his shoulders and chest, something wrong with how the light hit them, like the surface was always slightly wet — and it was streaked with blood and viscera that he hadn’t cleaned off. The linen underneath had soaked through at the collar and gone dark. His forearms were armored with vambraces and stained to the elbow, and there was a smear of dried blood on his cheekbone that had cracked at the edges and gone almost black. He had the face of a man who hadn't slept and wasn't thinking about it — jaw set, eyes forward, and mind clearly elsewhere.
The guard spread out around them without being told, and even Elroy and Jenkins weren't making noise, that told told Finn more about the mood than anything else could. They walked for twenty minutes in silence through streets that smelled like smoke and copper and wet grass, and Finn spent the whole walk abandoning every version of his opening line one by one.
He hadn't settled on one when they came around the supply wagons and he saw the pile.
Lizardmen bodies were stacked in two rough rows along the south wall, and three legionaries crouched among them with their sleeves rolled up and ceramic collection jars lined up beside them. One was working at a lizard's face with a short blade, unhurried, extracting something pale and spherical from the socket. The second had a lizard draped half across his knee, pressing something out of a gland along its neck the way you'd pit a cherry.
Harold crouched beside the nearest body, pulled a jar from the line, and got to work.
Finn stood there, trying to remember how breathing worked.
Henri was three paces to his left, arms folded, watching Harold work with a look of disgust.
"Shut your mouth," Harold said, not looking up. "The flies."
Finn shut his mouth. Henri, to his credit, already had his shut and kept it that way.
"What are you—" Finn started.
"We need their eyes." Harold held one up — a dark amber disc, pupil a vertical slash, about the size of a copper coin. "Darkvision potions. We'll need it eventually." He set it in the jar and moved to the jaw without pausing, pressing along the gland line with two fingers. "Venom sacs in separate containers, labeled. The gland Optio Cress is working on is a mana inhibitor. The spinal fluid is what I actually need you here for." He found the access point and began using a knife professionally, but when he got to work and murmured, his voice had a quality when he was mostly somewhere else.
"Mana helps with this part. Nice to have it this time."
A faint sound as something gave. "Bodies come apart cleanly if you know where to ask."
Henri's eyes widened. He didn't say anything, which was, Finn thought, the single most disciplined thing he'd seen Henri do.
Finn's brain had been running chemical breakdowns since the moment he'd seen the jars lined up, which was the only reason he wasn't embarrassing himself. Organic compound extraction from novel biological sources, he told himself. Normal. Very normal.
"Is there a reason," he said carefully, "we're doing this in the courtyard, and not, like, anywhere else."
"Convenience mostly," Harold said.
"Right." Finn crouched across from him, set his bag down, and picked up a spare blade from the kit without being told. "So the spinal fluid — what's the application?"
"Sleeping compounds work on about forty percent of lizardmen as-is. The rest have enough mana resistance that a generic compound passes through before it can bind." Harold tilted the body's head back, found the access point with two fingers, and his eyes went to the middle distance for a moment in the way they did when he was working and thinking simultaneously and the thinking had mostly won. "Neural fluid has biological markers native to their physiology. We use it as a base, and the binding agents get a key their mana resistance can't flag as external." He extracted it into a jar and sealed it without looking at the jar. "Follow that?"
"You're using their own biology to get past their own defenses."
"Exactly." He moved to the jaw, worked a venom sac free intact, and lowered it into its own container. "Their venom is a very very weak mana, disruptive in its raw form. We refine it about a million times to get any use out of it. Eyes in a third set — darkvision compound, just good to have." He glanced at Finn. "Help Cress. As many eyes as we can get, and we have more bodies coming."
Henri unfolded his arms, refolded them the other way, and whispered, horrified, to no one in particular: "He is enjoying this."
Finn looked at Harold — blood smeared on the cheekbone, forearms already dark with what he was working in, talking through extraction applications in the same tone he used to explain a distillation sequence — and didn't say anything, because Henri wasn't wrong.
Finn moved to Optio Cress's row. Cress shifted without looking up.
He took a breath and positioned the blade. The first eye, he fumbled, and the socket slipped. The second try, he nicked the disc and felt Harold glance at him from ten feet away without turning his head. The third try, it came out clean.
Harold had done four in that time.
First semester grad lab, Finn thought, with the specific misery of someone who remembered being the worst in the room. It's fine. It's the same principle.
It was absolutely not the same principle.
He'd had Harold's alchemy classes. The informal ones, where Harold perched on a table and talked through compound interactions like he was describing something that delighted him — stopping mid-sentence to ask questions nobody expected, making dry jokes about the students who weren't paying attention, getting animated about reaction cascades and extraction timing. Those classes had been the best part of Finn's week. He'd started showing up early.
He studied the man crouching over a dead lizardman with blood on his forearms and a smear of it drying on his cheekbone, working through the body with the ease of someone who'd done this enough that the specific type of body had stopped registering as remarkable, and thought: that guy and this guy cannot be the same.
"The greymantle," Harold said. "Where is it?"
Finn reached into his bag and found the piece Renna had passed him twenty minutes ago — dense, pale grey, almost iron-heavy for its size, with a crystalline structure inside that shifted when the light hit it right. He held it out.
Harold took it without looking, turned it once, and set it beside his knee.
"Lady Renna," he said, with something in his voice that wasn't quite amusement but was close enough to be its neighbor. "Do you know how she got this?"
"She said she bought a painting."
"She bought a painting," Harold confirmed. "Off a man with a studio in the artisans' quarter that hasn't had a customer in a while — these people don't have much coin left for good art. He paints landscapes. The kind of work you stand in front of for ten minutes and keep finding things in." He pressed along the jaw, found an angle, and extracted a venom sac intact. "She walked in, spent fifteen minutes with everything on his walls, bought a river valley piece with a wrecked mill in the background and about forty things hidden in the treeline, paid him in actual coin — not the barter he usually gets — and he liked her for it enough that he threw in the greymantle when she noticed it on the windowsill." A beat. "It was sitting there because dwarves had once tried to trade it for a painting. He took it because it was pretty and had no idea what it was worth."
Finn looked at the piece. "What is it worth?"
"More than the painting." Harold picked it up again. "Greymantle forms in deep cave systems where mana has pooled without disturbance for decades. The crystalline structure absorbs ambient mana and releases it back extremely slowly — like a sponge that fills in an hour and drips for a week." He set it down. "Dwarves figured out that an imbuer can work that property into metal. The metal takes on the same slow-release character, which means anything reactive inside gets held in a kind of dampened stasis. Slowed to the point where it can be stored and transported."
Finn's hands went still on the extraction blade. "It's not a stabilizer."
"No. A stabilizer interrupts the reaction — that's why mana control matters, because you can maintain potency while halting progress. Greymantle doesn't interrupt anything." Harold moved to the last body in his row. "The reaction still happens. It just happens at about one percent of the speed." He glanced up. "How far out is the third wave?"
"Colonel Hale said maybe six hours."
"Then we have four hours." Harold stood, stripped off his gloves, and looked at the row of sealed jars along the wall. "Twelve eyes?"
"Eleven," Finn said. "Twelfth cracked."
Harold looked at him. Then at the jars. "That's enough. Grab the spinal fluid jars and bring the greymantle."
The smith's shop was just off the main square — a long stone counter cleared of everything except Harold's drawing, a set of bellows still warm from the morning work, and a housing that had taken the smiths a full day to build from Harold's specifications. It looked, to Finn's eye, like an extremely overbuilt barrel made of dark iron with a sealed base and a trigger mechanism on one end he didn't understand yet. The size of a wardrobe laid on its side, thick-walled, with four carrying rings bolted to the base. Two of Aldric's militia stood nearby nervously.
The imbuer was already there — a young man named Jessim who looked about Finn's age, maybe a year younger, with ink-stained fingers and the posture of someone who'd been asked to do something he wasn't sure he could do. He had a greymantle fragment on the counter in front of him, turning it slowly.
"I've read about greymantle," Jessim said, when Harold approached. "Never worked with it." He set it down. "The imbuement process should transfer the slow-release property into the metal, but the binding pass is going to be delicate — greymantle resists initial contact, you have to coax it rather than push." He glanced at Harold, then away. "That's what I've read, anyway. I'm not sure I have the skill for this, my lord."
Harold looked at the housing. Then at Jessim.
He didn't say anything for a moment, and Finn felt it before he understood what it was — a change in the weight of the air. His spine straightened on its own. Across the counter, Jessim's shoulders came up and then, slowly, back down.
"You read correctly," Harold said, in the same tone he used to explain a distillation ratio. "I don't know much about imbuement. I know it takes enormous will, where alchemy takes enormous control." He looked at the housing and shrugged, and the shrug was unbothered. "If you want something to motivate you — this town, your home, will likely fall, and your family and everyone you have known your whole life will be killed, if we cannot complete this." A beat. "Barbaric thing to say out loud, but we don't have time for a softer version. Either you succeed, or we all die." He paused. "In roughly two hours."
Finn's mouth dropped. He closed it.
Jessim looked at the housing for a long moment, then picked up the greymantle, turned it once in his fingers, and nodded.
"Right," he said. "I'll need the side panels off."
Harold looked at the smiths. One of them was already moving.
"Ninety minutes," Harold said, and turned to the counter.
Finn let out a breath he'd been holding for what felt like the last two minutes and looked at Harold nervously — blood dried on the cheekbone, forearms still bloody from the courtyard, explaining the stakes to a terrified apprentice with the exact same calm he'd used carving into lizard bodies.
"Right," Harold said, pulling jars from Finn's bag and laying them out in an order Finn couldn't yet read the logic of. "Let's talk about what we're building and why it's not a gun."
Finn looked up from the housing.
"Every Earth person eventually asks why nobody's made gunpowder," Harold said. "The answer is that they have. Dozens of times. And it never works." He looked at Finn directly. "Does it?"
Finn opened his mouth, closed it, and felt his face do something he didn't love. "I — those were controlled experiments. I had a containment protocol. I wasn't trying to actually—" He stopped. Started again. "How did you know about that?"
"Because you're you." Harold went back to the counter. "Also, your containment protocol left a scorch mark on the ceiling of the prep room that Adeline reported to me six weeks ago." A beat. "But mostly because you're you."
Finn looked down. There was, in fact, sulfur residue smeared on his left boot. He'd forgotten to clean it off.
"It never stabilized," he said, since apparently they were having this conversation. "Didn't matter what ratio I tried, what I changed — the reaction would run for half a second and then collapse. Or spike, and I'd have to dump the whole thing in the containment vat."
"Right." Harold unstoppered the first jar. "Everything here has mana inherent to it — every material, every compound. It's not inert the way chemistry assumes, and mana doesn't behave in chemical reactions. It alters them. Gunpowder requires a very specific, very fast oxidation reaction, and the moment you introduce materials with ambient mana, the reaction changes. Sometimes it accelerates, and you have an explosion in your hands. Sometimes it dampens, and you get a slow burn that goes nowhere." He looked at Finn. "What does that tell you?"
"You can't stabilize the reaction if the variables are mana-influenced rather than chemical," Finn said it faster than he meant to, because he'd been thinking about this for six weeks and it was annoying him. "And they're worse than biological variables because at least biological systems have evolutionary consistency. Mana concentration varies by location, by material origin, by weather, by how many mana-capable individuals are standing nearby — it's not a constant, it's a moving target, so any formula you build assumes a baseline that doesn't hold."
Harold's hands slowed on the counter for about half a second. "Yes," he said. "Exactly that." He went back to measuring. "Dwarves cracked it somehow. Won't share it, and they've been known to go quite far to keep it that way." He paused. "So we're not making gunpowder."
"What are we making?"
"We are making," Harold said, picking up a grinding stone, "a big fuck-off bomb." He started working the bowl. "The components will react violently when combined — normally, that reaction would be too fast to control, it would detonate the moment the ingredients combined in enough quantities. We’ll use two separate chambers in the housing to keep it separated, trigger mechanism breaches the wall between them when we're ready." He nodded toward where Jessim was working. "The greymantle slows the reaction as the materials combine. Depending on how well our imbuer does, we should get about thirty minutes from trigger to detonation. The math is hard because it will speed up exponentially as they combine — but the delay actually makes it more powerful, since more material combines before the reaction runs to completion."
Finn stared at the housing. "You're letting the reaction run longer in a contained environment to increase yield." He said, horrified. ‘That’s what I did, and Sela died!”
"Mm." Harold added something that smelled sharply of sulfur. "We place it ahead of the third wave's formation, trigger when they're twenty minutes out, and we're back inside the walls before it goes off."
Finn did the math. It took him about four seconds. "That timing has almost no margin."
"Ehh, twenty minutes of margin."
"That's — okay, twenty minutes." He pulled in a breath. "And the sleeping potions, you said earlier—"
"Are for the next phase." Harold set the bowl down in front of him and pointed at the second set of jars. "The neural fluid batch is a ton of work, but it'll be worth having when we need it. Grind those two together in that ratio and fold it into what's already in the bowl." He held up a finger. "Don't rush the fold."
Finn took the bowl with both hands and settled at the counter. He worked carefully — the way Sela had always insisted on, the way he hadn't always listened to the first time she'd said it. He was listening now.
"How big is the blast radius?" he asked.
"At this volume?" Harold held a flask up to the light, watching the color. "Roughly three times the size of what you made. Luckily, this potion is extremely simple. It’s the only reason I can do it. Just a matter of scale."
Finn looked at the housing. "That will kill a lot of them."
"That's the point."
"How many do you think—"
"Stop counting and keep folding." Harold set the flask aside. "Even color, no separation?"
Finn checked the bowl. "Yeah."
"Good. Set it aside." Harold looked at the housing, at the counter, and then said, mostly to himself, "Not enough time."
He crossed to where Carter had positioned a large ironwork cauldron — field cooking size, wide-bellied, black with long use — and dragged it to the center of the workspace with one hand. Then he went to the supply chest they'd hauled from the Landing, the just-in-case one, and started going through it with both hands.
Finn watched him pull out jars, bundles, sealed cases, setting some aside and keeping others. Then Harold stopped, reached into the bottom of the chest, and pulled out a large canvas bundle tied with twine. He cut the twine and unrolled it on the counter.
Finn saw the leaves inside, counted them without meaning to, and felt something cold drop through his chest.
They were the same leaves used for explosive potions. One medium-sized leaf per potion, per the formula. Harold's formula.
Harold had hundreds of them, and he picked up the bundle and tipped the entire thing into the cauldron.
"Lord Harold—" Finn's voice came out smaller than he wanted. "That — there's no way to control that reaction at that volume, the cascade alone would — the heat bloom before primary ignition would trigger the secondaries before the binding agents even—" He stopped, because Harold wasn't stopping, and explaining the problem wasn't going to change what was already in the cauldron. "Wait. What are you — how are you planning to—"
Harold set down the last container and looked at him with the specific patience of someone who'd already solved the problem Finn was currently describing. "You might want to back up. This part is going to be hard."
Finn backed up. Carter appeared from somewhere and moved him back another three steps without discussion, one hand on his collar.
Harold placed both hands flat on the rim of the cauldron.
Finn had watched Harold make potions in the hall. The control — the way he'd thread mana through a compound, each pulse measured, his attention moving through the ingredients precisely. He'd been impressed by it. He'd tried to reverse-engineer the technique from watching.
This was not that.
The mana that came off Harold hit the air like a physical weight, pressing against Finn's chest from fifteen feet away and not stopping. It wasn't threading. It was Harold putting all of himself into the contents of the cauldron and forcing them down from every direction, a single massive force driving into the mixture while a dozen thinner threads moved through it simultaneously, each one doing something Finn couldn't track fast enough to name. Each pulse drove Harold back half a step. Each pulse, he leaned back into it, hands locked on the rim, and did it again.
Finn took one step forward.
Carter's grip tightened on his collar. "Don't distract him, or we all die."
He stayed. He couldn't look away. The Thresher King's armor shifted on Harold's shoulders with each pulse — deep grey-green scales that caught the light wrong, something underwater in how they moved. His face had stripped down to nothing but the work — jaw set, eyes open and fixed on the cauldron interior with intensity, the place past focus where a man stops tracking anything except the one thing in front of him. The blood on his cheekbone had dried dark and cracked at the edges, and with each pulse, a fine tremor moved across his skin over the bone in time with the mana output, pulling tight and releasing, tight and releasing, like his whole face was part of the mechanism and his hair was swirling around him.
He looked, Finn thought, completely and genuinely unhinged, and also like he was exactly where he wanted to be. His eyes were alight, and a rictus of a smile was on his face.
Twenty minutes — he counted without meaning to, the way he'd once counted pulse times on a reaction timer in a university lab — twenty minutes of Harold at that output, at that precision, running simultaneously in the same pair of hands while the mixture in the cauldron slowly, slowly resolved into something that should not be holdable.
What is his mana capacity, the part of Finn's brain that wouldn't stop doing chemistry kept asking, because the output he was watching was insane.
Harold's hands came off the rim, and he took one step back, and his knees went, and Carter caught him under both arms before he went down. Harold didn't fall — Carter didn't let him — but he didn't stand either, just hung there with his head dropped forward and his breath coming in long pulls through his nose.
Carter walked him back to the counter and sat him against it, hand on his shoulder. Harold's face had gone grey under the blood on his cheekbone. His hands were shaking, and he pressed the heel of one against his eyes and said nothing for thirty seconds.
"Give me a minute," Harold said. His voice came out rough and about half volume.
Carter looked at Finn, and the look was unambiguous: don't.
Finn looked at the cauldron, sitting still and stable on the floor, holding something that should not be holdable, and looked at Harold slumped against the counter with his face the color of old ash and his hands still trembling, and said, very quietly, to nobody in particular: "What the fuck."
Harold, eyes still closed, said: "That'll hold until we get it into the housing. We just need Jessim to finish."
Finn looked at the cauldron. He looked at Harold. He looked at the cauldron again. He’d spent three years studying thermodynamic reactions, and he thought he had been learning how all this worked, and Harold just made sure he knew that he understood nothing.
"I want to ask so many questions right now," he said.
"Later," Carter said.
"There are like twelve separate things happening in there that shouldn't be—"
"Later," Carter said.
Jessim finished ten minutes after that, stepping back from the housing with greymantle dust on his forearms. He looked at Harold sitting on the floor against the counter and opened his mouth, then closed it.
Harold opened his eyes, pushed himself upright with one hand on the counter's edge, crossed to the housing, and pressed two fingers flat against the metal for three seconds.
He nodded once without looking at Jessim, and Jessim's shoulders dropped half an inch.
"Get Ren and Corwin." The clipped edge was mostly back in his voice. "That mana lock isn't permanent — we've got maybe two hours before it starts degrading, and the reaction wants to run. Get the compound into the housing, arm the mechanism, and make sure the separator plate is seated before you trigger the arm so the mixtures stay isolated until we want them together." He pushed off the counter, and his knees held this time. "Do not let anyone rush the separator plate. That plate is the only thing keeping this from being a very short conversation."
Carter was already moving, two fingers up across the stall. "Separator first, arm after. Anyone touches that trigger pin before I say so loses the hand. And keep Elroy and Jenkins away."
Elroy appeared at the entrance to the stall, Jenkins a step behind him. Neither of them was doing the thing they usually did. Elroy looked at the housing, looked at the cauldron, looked at Harold slumped against the counter with his face still grey, and said nothing for a moment.
He looked at the housing again, and his jaw was set in a way Finn hadn't seen on him before, and his eyes had something in them that wasn't a joke.
"Tell us where you need us," Jenkins said. His voice was flat and even, and it didn't sound like Jenkins at all, and then Finn realized it did; he was just serious for once in his life.
Carter looked at them both for half a second. "Grab us an escort to get this out of the town."
"Understood," Elroy said, and they left, and the stall was quieter than it had been.
Henri watched them go. "I did not know they could do that," he said.
"Most people don't," Carter said.
He glanced back at Harold. "Sit back down."
"I'm fine."
"You're grey."
"I'm always grey, Carter, I'm tired."
Finn stood with his arms crossed, watching Harold and Carter argue about whether Harold's legs were working, and his brain, still running chemistry calculations quietly, noted that the greymantle imbuement had performed within expected parameters and the cauldron contents appeared to be exhibiting a controlled exothermic profile, and then he noticed his hands were shaking a little and understood that this was fear finally landing after the fact.
"Lord Harold," he said.
Harold looked at him, exhaustion writ on his face.
"When this is over," Finn said, "I want to know every step of what you just did. All of it. Written down, if possible."
Harold looked at him for a moment, and something shifted in his face — not warmth exactly, but recognition, the expression of someone who'd been asked the exact right question and had noticed. "Buy me a beer first," he said.
"I'll buy you three."