Zhang Haike tilted his head back, carefully leaned down, and brought his head close to the copper horse. After adjusting his position, he let out a sigh of relief and reached for his waist, where he had a bottle of “cha zi shui,” a type of mixed strong acid. After opening it, he cautiously dripped some onto the back of the copper horse.

The strong acid immediately began to corrode the horse’s back, quickly eating away a large area and revealing the internal structure. Zhang Haike put away the “cha zi shui,” lit a fire starter, and leaned in to examine the exposed area. Indeed, the internal mechanism was complex; he could see hundreds of tightly stretched wires, with a small round disk on one of the wires filled with small iron beads.

The small iron beads were heavily rusted and mottled, resembling the surface of the moon, but it was still possible to discern that they were originally engraved with intricate patterns.

“What kind of mechanism is this?” someone nearby asked.

“A variant of the eighteen-string mechanism, much more complex,” Zhang Haike replied.

Beneath that disk was a balance device invented by Lu Ban. Even the slightest vibration would cause the disk to tilt, but as long as the weight of the disk changed, the small iron beads would roll out, and the disk would immediately return to balance. The beads that rolled out would hit the wires below, bouncing along, with each wire triggering a mechanism. There were hundreds of wires here, and depending on which wires were touched, seven or eight different mechanisms could be triggered at once.

After that, the disk would restore its balance, meaning it could be triggered multiple times, with each triggering being random and completely unpredictable. Such mechanisms were said to have been invented by Lu Ban, with eighteen variations. Later generations added to it, and Zhang Haike had once seen a mechanism with seventy-two wires, crafted by an old gentleman to demonstrate the function of the eighteen-string mechanism, but this was the first time he had seen one with hundreds of wires.

Zhang Haike let out a breath of relief, grateful that he had taken this seriously and used the most troublesome yet safest method. He turned to ask the person holding the steel cable if they could still hold on, and after receiving a positive response, he held his breath, lit the fire starter again, and took out a magnet from his pouch to place above the disk. All the small iron beads were immediately attracted to the magnet.

He then carefully moved the magnet away, stowed it in his bag, and climbed down the steel wire to land on the ground next to the copper horse. The moment he landed, he saw the disk instantly respond to the vibration and tilt slightly, but since there were no iron beads inside, nothing happened.

The group remained silent for a moment, realizing that nothing had actually been triggered, and they all let out a sigh of relief. One of them said, “That was easy.”

Zhang Haike glanced at the iron beads on the magnet, noncommittal. He was not skilled at dealing with such mechanisms, especially in a real ancient tomb, but it seemed that this time he had won the gamble.

They packed up their things and prepared to continue searching. One person suggested, “Should we call that little ghost down?”

“Why call him down? He can’t do anything and we have to take care of him. Plus, he doesn’t think much of us. Let him stay up there,” another replied. “Let’s finish our business quickly.”

Zhang Haike thought for a moment and nodded. He didn’t think that the “dumb oil bottle” was a burden; rather, he felt that this was just the first mechanism they encountered in the tomb, and it was already so complex and sharp. They still didn’t know what other situations were like in the tomb, so he felt that being overly confident was a bit premature. The “dumb oil bottle” could still provide a lot of convenience from above.

The few of them approached the bronze horse, all of them seeing the “eighteen strings” mechanism trap for the first time. They looked into the molten hole and revealed expressions of astonishment at the densely packed threads inside. Zhang Haike couldn’t help but feel a bit proud—this mechanism was something he had deciphered, without any errors, and he felt quite accomplished. At that moment, someone suddenly asked him, “There are hundreds of threads here. Does that mean there are hundreds of mechanisms in this room?”

“What’s wrong?” Zhang Haike asked.

The speaker lit a match and threw it around the tomb passage, quickly illuminating the corners of the tomb. He said, “How could there possibly be that much space here?”

Zhang Haike turned to look around the tomb, and indeed, most mechanisms in ancient tombs were large in size. The reason it was called “eighteen strings” was that eighteen different mechanisms already represented a limit in volume. The various mechanisms added later were mostly just variations of these eighteen types. For example, if one string could trigger quicksand, then it could also give rise to variations like poisonous smoke, mercury, and other mechanisms. However, if there were so many threads, it was clear that it couldn’t be explained by simple variations.

“What do you think?” Zhang Haike realized that the other person’s observation was correct.

“It doesn’t seem like there are hundreds of different mechanisms being activated. I think these hundreds of threads are all connected to the same mechanism but trigger different parts of it,” the person said. “It’s like the foreigner’s puppet on strings; the threads move the same puppet, but different strings move different parts of the puppet, which explains the issue of space.”

“Are you saying that after we trigger this mechanism, a puppet might appear?”

“I’m just using it as a metaphor,” the person said. “But I believe that the consequences of triggering this mechanism might be different from what we imagine; perhaps it’s not an offensive mechanism.”

“What could it be?” Zhang Haike asked.

“I don’t know. We can only find out after we trigger it,” the person said, touching the four legs of the horse. “All the threads connect through these four horse legs to the ground, and then radiate underground, connecting to the mechanisms in this room. The mechanism room is located in the area right beneath our feet, and the force of the iron ball hitting the threads is not great, so this transmission mechanism will surely be amplified in the underground mechanism room. Now, let’s simulate the construction process of this room and see if we can get down to the mechanism room; this would give us more confidence about this room.”

The man finished speaking, and Zhang Haike felt that something was amiss. He looked at the tunnel they had come down: “When we opened the wall, we didn’t see any mechanisms inside, so all these hundreds of changes must be beneath our feet. It’s too dangerous to dig back into the tomb chamber; we need to go outside and start digging down from the soil again. This will take a long time, and if there’s a layer of Qionggang stone beneath the tomb, we might not be able to break through for a whole week.”

The group felt a bit deflated, and one of them said, “After all this analysis, are we being too cautious? How about this: we go up into the tunnel, take a small stone, and tap these threads to see what happens. If we keep discussing, we’ll scare ourselves to death.”

Zhang Haike listened and thought this method was feasible; they had indeed spent too much time in the tomb chamber and needed to make some progress.

The person who suggested going back into the tunnel lit a fuse and placed it at the gap of the copper horse, while several of the Zhang family children turned back and climbed into the tunnel. The muffled oil bottle was at the bend of the tunnel, remaining silent, but it was clear he had heard everything that had just been said, making the Zhang children feel somewhat embarrassed.

The fuse didn’t burn for long. Once everyone was up, Zhang Haike took an iron ball from his bag, flicked it with his finger, and shot it towards the glowing spot of the fuse. The iron ball zipped through the flames and struck inside the copper horse, followed by a series of faint clattering sounds. Everyone held their breath, waiting for the mechanism to activate.

The Zhang family had excellent hearing. After holding their breath, everyone heard a series of rustling sounds, so faint that it was impossible to tell where they were coming from; an ordinary person certainly wouldn’t have heard it.

Three to five seconds later, suddenly, the entire tomb chamber shook, and everyone saw the ground’s blue bricks change.

In four places on the ground, the blue bricks had sunk in.

Zhang Haike quickly tossed out the fuse, and under the flickering light, they discovered a downward passage had appeared on the ground.

The passage seemed to be very steep, more like a deep well leading underground.

“Unseen and unheard, what on earth is this place?” Zhang Haike muttered to himself, “What kind of mechanism is this?”