The Tracking Cart. Since it was designed to track, it moved automatically. Its power came from a golem core, and the source of that power was magic stones.
Magic stones are jewels imbued with magic power, harvested from defeated magic beasts and monsters. The stronger the creature, the larger the stone, the higher its magic density, and the better its overall quality. In other words, large magic stones are incredibly precious.
Because of this, the Tracking Cart was initially designed to run on small magic stones. However, making it function with such small power sources required various clever workarounds. While these technical gymnastics were usually the Mountain Elves' specialty, they unfortunately became a major bottleneck for mass production. It was the kind of master craftsmanship that only a few people could pull off.
The Mountain Elves eventually came to a realization. If they stayed on this path, they would be completely consumed by the mass production of Tracking Carts and wouldn't be able to invent anything else. So, they decided to throw those clever tricks out the window.
Specifically, they abandoned the idea of using small stones in favor of large ones. Their new policy was to brute-force the mechanism using the raw power of larger magic stones. This simplified the internal structure of the Tracking Cart significantly, making mass production a viable reality.
The problem, however, was securing enough large magic stones. As I mentioned, they are quite valuable. The small stones we used initially were about the size of a halved watermelon seed. The "large" magic stones the Mountain Elves were now asking for were roughly the size of a pinky nail. Collecting enough stones of that specific size looked like it would be a struggle.
We did have a stock of magic stones in the village storehouse, accumulated every time Kuro and the others went hunting. Kuro, Zabuton, and the rest used to enjoy eating them, but lately, they had been complaining that the stones were a bit too hard. They seemed to be losing their appetite for them, preferring meat and potatoes instead. Consequently, the stockpile just kept growing.
I wondered if we could use those stones for the Tracking Carts, but the magic stones in our storehouse ranged from the size of a thumbnail to the size of a basketball. They were apparently too big. While they could be used, the stones themselves were so valuable that the carts would become far too expensive to sell.
I suggested simply crushing them down to size, but the Mountain Elves stopped me immediately, insisting it would be a terrible waste. Lu and Tia nodded in agreement.
It seemed large magic stones really were precious. And yet, I had used plenty of stones around ten centimeters in diameter for the automatic vending golems. Furthermore, when Yor mentioned she wanted magic stones as material for ammunition, I had handed over several baseball-sized ones, which she ground into powder without a second thought.
I decided it was best not to mention that to the elves. I would keep that secret to myself.
In any case, our top priority was collecting magic stones about the size of a pinky nail. I placed an order with the Goroun Company and the Dalfon Company. For payment, we agreed to swap weight for weight—equal total mass of stones, regardless of size. I wondered if that was a fair deal, but both companies were ecstatic, calling it an extraordinary offer. I suppose there was no issue, then.
We had already completed two exchanges with the Goroun Company and three with the Dalfon Company. In total, we had only handed over five ping-pong-ball-sized stones. I offered to throw in even larger ones as a bonus, but they refused with everything they had.
Then, Domaim arrived at the village. As an omiyage, he delivered a massive quantity of huge, light-green rocks, each about a meter in diameter. There were enough of them to form a small mountain. I was grateful, but I had no idea what they were for.
"Uh, to be honest, I don't know either," Domaim admitted. "Lananon-sama simply said that you would be pleased if I brought them here."
Lananon? Ah, he meant Lana-san. Since my daughter has the same name, she’s always the first one who comes to mind. It’s a bit confusing. Regardless, if Lana-san sent them, these rocks had to be useful to the village. Since I didn't recognize them, I decided to ask someone who might.
Lu was busy manufacturing parts for the Tracking Carts, and Tia was with her. That left Dos. I asked him, but he didn't seem to recognize them at first.
"Ah, no, wait," he said, something catching in his memory. "These rocks... I saw them in Gulgrant-sama’s treasure room!"
I remembered the key to Lana-san's husband's vault that she had given me. Dos knew where the treasure room was, but it was currently located on the seafloor. He had refused to take me there because he couldn't guarantee my safety. If Dos said it was dangerous, it really must be. I hadn't pushed the matter.
Dos was currently holding the key and having his subordinates retrieve the contents for me. He had gone to open the vault and returned, but the items hadn't reached the village yet because he needed to verify the contents before handing them over. If these light-green rocks were in that vault, there was a high probability they were related to Artie Horses. If that was the case, it made sense why Lana-san thought the village would be happy to have them.
I didn't know exactly how they were related, and neither did Dos. I wondered if showing them to Yor would help.
"There is no need for that," Bell said, stopping me from calling for Yor. She was visiting the village and suggested I call Lu and Tia instead.
I pointed out that they were both very busy.
"Even if it delays their work, it is better that they know now," Bell insisted.
I took her word for it and called for them. When Lu and Tia saw the mountain of light-green rocks, their faces visibly twitched. Was this stuff that rare?
"It's not so much that it's rare as it is..." Lu began, but Tia quietly stopped her.
Tia then fetched a baseball-sized magic stone from the storehouse and used one of the light-green rocks to craft a golem. It looked different from the usual ones. It was an Artie Horse—specifically, a replica of Unit No. 1 from before it had been absorbed by Crim.
"I modeled it this way because it’s easy to recognize. It's just an exterior shell; the inside is completely hollow," Tia explained.
"I see."
"These rocks are called many things, but I call them Magic Composite Iron."
Its primary characteristic was its ease of processing, as evidenced by how perfectly she had replicated Unit No. 1. The color had even shifted. Then there was its expandability. From a single meter-wide rock, she had created a hollow shell ten meters tall. It had expanded significantly.
Despite the size, the weight remained identical to the original rock. It was incredibly light, yet remarkably hard.
"With this, we can repair the Artie Horses' armor and replicate parts with ease," Tia said.
That was a huge relief. It meant we could handle minor repairs for the machines ourselves. It definitely qualified as an Artie Horse-related item. However, nothing in this world is purely convenient. I asked if there were any downsides. Was it weak to heat? Flammable?
"No. Magic Composite Iron and the things made from it have no real weaknesses to speak of. However, handling it requires a specific level of skill and a massive amount of magic power."
It required so much power that Tia had to use a magic stone just to shape it.
"Yes. And then there's the cost. I heard it was once abundant, but now it's quite precious. There are very few people left who know how to work with it."
Apparently, a single meter-wide rock of the stuff was worth as much as the baseball-sized magic stone Tia had taken from the storehouse. And we had a small mountain of it.
"We should store this in the storehouse... actually, let's ask Ria and the others to build an extension," I suggested.
"Wait a moment, Tia," Lu interrupted, looking at the replica of Unit No. 1. "This material has a very specific weakness, doesn't it?"
Tia tilted her head, seemingly confused.
"It's so hard that it cannot be re-processed," Lu explained.
"Ah, that’s right."
Apparently, once you expand it and set its shape, it's almost impossible to change it again.
"But surely that’s an advantage rather than a weakness?" Tia argued.
I agreed. Being difficult to tamper with or break seemed like a benefit to me.
"Is that so?" Lu asked. "Then what are you going to do with this Unit No. 1? You didn't build it with the ability to move, did you?"
...
Unlike a normal golem, it couldn't be reverted to its original state. It couldn't be re-processed. And it was incredibly hard.
I looked at Tia. She thought for a moment, then turned toward me with a very troubled expression.
Well, she’d been busy lately. It was an easy mistake to make. I made sure to offer her some support.
The Unit No. 1 imitation made of Magic Composite Iron stood valiantly in the village for a while until the Mountain Elves finally dismantled it. It was light enough to move easily, which was a small mercy.
Domaim: "It's been forever since I had a turn, and I couldn't even keep up with the conversation..." Hakuren: "Don't worry, there'll be some follow-up for you next time." Bell: "I thought it was finally my time to shine..." Yor: "That’s because you keep stealing my spotlight."