In the Rising World workshop, Vonn and his team puzzled over a disturbing bag. That adventurer team led by the careful man named Spikes had been the ones to propose it. The bruise-purple cylinder on the table now was the preserved gullet of one of the sonic monsters the dungeon kept generating.

Birb looked up from measuring the fleshy thing with a crude pressure gauge. "It's not leaking yet." One of the twin Kobolds working a bellows nearby had pumped lots of air into it. There was also a rod spearing the thing, making it look like a piston using a leather bag instead of a metal cylinder.

Vonn should have seen the possibility sooner, of using monster parts for his work. He'd crashed an airplane into the dungeon, after all, and these places imitated things that people lost there. The sound-screaming toad monster had a throat good for air pressure control. So he'd bought one from the delvers. He'd tried to invent bagpipes and instead discovered the whoopee cushion.

"Good chance for you to try out this new power," Vonn said to Birb. "Go on, seal it properly."

The bird girl concentrated, her feathers fluffing up nervously at all the attention. She applied a glue of Selen's design to a stitched-up incision, and managed to get the piston rod inserted in a way that would slide without leaking air. There was also a needle with a tiny valve for using a pump to fill the thing, something the Company was considering doing for sports balls and bike tires. "Um. So this is where I'm using Harmonious Join, making the displacer piston efficient."

Vonn touched the device and inspected it, admiring the work that Birb and Tazo had done. There was little for him to add but to try activating Well of Energy, his personal ability. It worked; the device shimmered in a distinctive red-gold color for a moment. "So I count well enough as Chief Engineer. You now have what might be the world's best engine, Birb."

"An engine core, anyway." Birb let Tazo help with the next step, rigging the monster gullet into the familiar arrangement of rods and wheels that turned it into a power supply. Then they weighed the whole thing, and Birb chirped triumphantly. "Go on, Tazo!"

Tazo laid hands on the device and spoke a silly chant. When she let go, the device was supposedly sturdier for her having worked on it. "Nice. The weight is promising, well under what we're getting for a metal pressure cylinder. But now we need power and durability testing."

Vonn stood back grinning, his arms folded. "You're sounding like experts, both of you."

They'd built another small invention in the process of cranking out mass produced engines for Baron Bogstep. It sat in the hangar: a small cart. Vonn had avoided giving it a plow blade, because the vehicle could be seen as an anti-necromancy weapon. After all, the Bonefire Guild was his neighbor, the Guild was keeping the south villages' farmers paying them for zombie plow labor, and Vonn really didn't need to be on the bad side of that group right now. He had to keep developing his tech. Besides, the Baron in that area might intervene if Vonn tried to change anything.

So Vonn wasn't going to help those people quite so directly as to get them better plows. Yet.

They'd tried the cart out with one of the iron engines. That worked all right, trundling slowly along with a box of ingots for cargo. Or today, carrying Birb. Now they hooked up the new engine and gave it a while to heat and cool, from glowing crystals doing their work. The cart trundled out from the hangar with Birb sitting atop it, feather-smiling and trying to work the crude rudder they'd installed.

"What is that?" asked several townsfolk, stopping to stare.

"Oh, just a horseless cart," the girl said.

"You need to stop."

Vonn had been walking alongside it. "It's nothing to be afraid of."

"No really, you're headed for the steep area."

Vonn startled, seeing how he'd plunge into the river. "Birb, stop this crazy thing!"

She disengaged the engine, but they still hadn't gotten around to proper brakes. The cart was going faster than usual and the pilot was having trouble swerving.

"Somebody strong, please help turn this."

A Human ran up, laughing, and gave the cart a shove. For a moment Vonn feared the whole thing would tip over, but the guy had done it right and the cart now trundled along a safe path that'd let it slow and stop. Vonn thanked him, feeling sheepish. "Uh, that was a mostly successful test. Let's get back and do a formal power measurement."

Since they were already near the east dock district, he stopped by the general store. The Centaur lady there said, "This came yesterday."

A box had come, taking him both hands to heave onto a table. He paid his end of the delivery charge and since the shopkeeper was so interested, opened it right there.

Firefern had sent a toy engine. Just inches wide, it wouldn't produce significant power, but he'd figured out the basics of a one-cylinder piston and rotating shaft powered by lamp oil that dripped down from a tiny jar.

"A copy of your gadget?" asked the shopkeeper.

"A different design, but a good one. He was that intent on showing it off that he sent the whole thing instead of just sending me a picture." Vonn rummaged and found more stuff in the box. A letter including diagrams showing the "Firefern Cycle Engine", another letter with that merchant fox's handwriting peeking out on the edge, and several cloth samples. There was even a magicite shard radiating faint aqua light.

"Quite a haul."

Vonn nodded, and packed it up again to take to the shop. "Looks like the southern Engineer group is eager to cooperate with us. I'll have to send them more detailed designs in the next letter."

He was probably obligated to report this contact to the Duke as part of his research. It only occurred to him on the way out that the shopkeeper likely had standard orders regarding interesting mail, too.