Valens' eyebrow rose. "Can you?"
"Stronger, yes. Strong enough… That's not the point, though." He scowled for a moment. "Daurenja's a very clever man. Brilliant, really, a genius. But he's set his heart on getting his idea to work, and that limits him. Now me…" He shrugged. "It's not my idea, I'm not in love with it like he is. I'm quite happy to explore the possibilities of what his idea can do if it doesn't work."
Valens sighed. "You're not making sense," he said.
"Oh, I think it's perfectly simple," Ziani replied. "To make the volcano, you mix stuff together to make a powder, and when you set light to it, you get an eruption. According to Daurenja, it's like what happens when water falls on a crucible full of molten metal, only much, much stronger."
"I see." Valens sighed again. "What does happen?"
"Lots." Ziani smiled. "The crucible cracks, burning hot liquid metal flies everywhere. It can crack walls, punch holes in roofs. The water turns to steam, you see, in a tearing hurry. The steam sort of pushes everything else out of the way. I imagine Daurenja's powder works the same way, except it makes smoke instead of steam. But the principle's the same. It's strong enough to smash a brass pot with sides an inch thick. Daurenja wants the pot to trap the smoke so it's only pushing one way, pushing against a stone lying on top of the powder, so the stone goes flying through the air. He reckons it'd have many times the force of the biggest siege engine ever built."
Valens' eyes had opened wide. "Would it?"
"I don't see why not." Ziani shook his head. "But even if it does, that's not much use to you. Suppose I could make a strong enough pot. To set up a forge to make a hundred of the things would take six months to a year. We haven't got that much time."
"That's true enough." Valens drummed his fingers on the table. "But you…"
"I can't help thinking," Ziani said. "Dig a hole under the City wall and stuff it full of barrels of Daurenja's powder. Stop up the hole with rocks, but leave a little gap, just enough to poke a burning rope into." He drew a little closer, knowing he had Valens' undivided attention. "The problem with sapping under the City walls is that they're built on foundations of solid rock. You remember how we sabotaged the silver mines, to stop the Republic getting them. We packed the mine shafts with brushwood and set it alight, to burn through the pit props and cave in the roof. But even if you had the time to cut a tunnel through solid rock, how are you going to collapse it? Oh, there's ways, according to your miners. There have been accidents in the past, where sloppy practice left gallery ceilings weak and they've caved in. But it'd need a lot of time and effort to do it on purpose. When they built the City, they thought about sappers, you can count on it. They built the walls where they are because they reckoned it wouldn't be practical for an enemy to undermine them. And without some new ingredient, like Daurenja's volcano dust, they'd have been right. That's what I had in mind when we were talking to that old man."
Valens thought for a long time; then he said, "Nice of you to tell me about it, finally. I'd have been really quite upset if you'd kept it to yourself all this time."
Ziani looked at him. "You've met Daurenja," he said, and left it at that.
Valens nodded very slightly, as though he didn't want anybody watching to see. "He's your man, though," he said. "You can handle him. I don't see a problem."
"No." Valens looked up as he said it. "I can't handle him. He scares me. I'd have had him killed, except I don't know the recipe for the volcano powder."
Valens turned away, as though suffering from cramp. When he turned back, he said, "Make him tell you. If you need help; soldiers…"
"He'd die first," Ziani said with conviction. "He knows, he's dead anyway without the secret. No, the deal is that I help him make his stronger pot. When I'm doing that, he'll have to share the secret with me, I'll tell him I can't help him unless I know it too. Once I know, of course, the situation changes. We may even succeed. The stupid thing is, all Daurenja wants is the stronger pot; not money or power or anything like that. He just wants to make a pot that can throw big heavy stones. I guess you could call him a visionary." Saying the word forced him to smile. "So, let him have his pot. It'd come in very useful, I'm sure, in future wars, assuming there's anybody left alive to fight once we're finished here. But there's always someone to fight, isn't there? Anyway, that's nothing to do with me. I just want fifty standard-size apple barrels full of his magic powder, and then I can get my job done and go home."
Valens picked up a goose quill and sharpened it, slowly and precisely. I could have trained him to be a useful engineer, Ziani thought; he doesn't hurry, and his hands don't shake, even when he's shocked or disgusted. "Fine," he said. "If what you say is true, it makes sense, and I'm very pleased to hear we've got a secret weapon that can crack the City wall, because without one we'd be completely screwed." He looked down at the point he'd shaved on the quill. "Why didn't you tell me before?"
Oh well, Ziani thought, and said: "Because Daurenja knows something about me that'd get me killed."
"I see." The pad of his index finger, pressed gently on the point; just enough pressure to prove its sharpness without causing damage. "Who by?"
"You," Ziani said. "Among others."
"It must be a very bad thing, then."
"It is."
"Not something you'd care to tell me about."
"No."
Valens looked up. His eyes were bright, as though he'd just been crying, but his face was completely blank. "But I can't have you killed," he said. "I need you to take the City for me."
"You'd just have to find another way," Ziani said. "You'd have no choice."
A shrug; graceful, as if he was dismissing trivia. "And Daurenja knows this dark secret of yours, but he won't tell me because he needs you to make him a stronger pot. I need you to crack the City wall. You need him to tell you how to make the magic dust. I know Daurenja's a rapist and a murderer; in fact, I had the devil of a job getting out of doing something about it, but fortunately I have resourceful people on my side who can do wonderful things with legal technicalities. So here we are," he went on calmly, "all of us turning a blind eye to every form of evil under the sun, because we don't have any choice in the matter. Take me," he added, looking down at his hands. "I killed my cousin Orsea so I could marry his widow. I knew Orsea wasn't guilty of treason. The evidence against him was far too glib, if you see what I mean. I knew you were lying. But I had him killed, all the same. And now Veatriz and I are married, and we love each other, and as soon as this bloody stupid war's over…" He looked up. "I suppose everybody asks himself at some time or other, what wouldn't I do to get what I want? And the answer is, when I find out, I'll let you know. The depressing part is, I really don't care any more."
But Ziani shook his head. "If you found out the truth about me, you'd have me killed," he said. "After you've taken the City."
Valens smiled. "Do you really think so?" he said. "Of course, I'm in no position to offer an opinion, since I don't know what you've done. But you're a clever man, you haven't made this extraordinary confession just to cleanse your soul. You want to make a deal, presumably. Well?"
Ziani nodded. His mouth was dry, but he felt calm. The art of designing a mechanism lies in enclosing the components so that they can only move one way. "Very simple," he said. "If you find out… my dark secret… you won't have me killed until the siege is over and we've either taken Mezentia or given up in despair. In return, I'll build your siege engines and do everything else I possibly can. That's all. A stay of execution, not a pardon."