After waiting for a few minutes, there was no sound of rolling stones, and Xu Xin and the four stone statues emerged from the small hole.

Chang Yin slapped the wall again, and the originally concave hole gradually became shallower, and finally returned to its original flatness.

"I have obsessive-compulsive disorder. I can't stand leaving a hole in the wall." Chang Yin explained with his hands spread out.

Xu Xin pointed to the back, where several huge boulders blocked the way. "Looks like we can only move forward."

"Why, do you still want to go back?" Chang Yin glanced at the rolling stone behind him and said indifferently, "If you really want to go back, I can take you back. How can a stone block my way?"

Xu Xin understood. Chang Yin's ability seemed to be controlling rocks. While it might not be able to stop a rolling boulder, it could certainly break a stationary boulder into pieces.

"Are there any other mechanisms ahead?" Xu Xin asked.

"No more," Xue Lan held the little boy's hand. "Last time, until we got to the first door, there was only this one mechanism. The rolling stone only appeared three times."

Continuing forward, they soon caught up with the mutant cheetah that was lying on the ground waiting for them to catch up.

Xu Xin passed by the cheetah and subconsciously wanted to touch the big cat's head, but the cat easily dodged him again and then followed him silently at a distance of two meters behind him.

There was no other way, so Xu Xin could only touch the sleeping Coco's head on his shoulder. Coco twisted slightly, made a sound like a dream, and continued to sleep soundly.

The tunnel became wider and wider.

Xu Xin could already see a big door not far away.

It was a door similar to the entrance to a dungeon, but several times larger, as big as the gate of a castle.

They quickly arrived at the door. Chang Yin first tried it himself, but no matter how hard he slammed it, the metal door remained motionless.

Xu Xin looked up and found a downward-opening hole directly above him. The hole was about the same size as the rolling stone, and it was probably where the rolling stone came out.

At this time, the bat that had been signed earlier came in handy. Xu Xin turned the ring with his thumb, and the mutant bat appeared in front of Xu Xin.

"Huh? You have also contracted a bat." Chang Yin looked at the big bat with some surprise.

"Let's go to the cave above and see if there's anything we can bring down." Xu Xin first directed the bat to fly into the cave above before answering Chang Yin, "It would be much more convenient to have a flying bat."

"Hmm... indeed, but the strength of a single bat is very average. It takes a lot of them to be effective."

After asking, Xu Xin learned that these bats were actually just failed products of Chang Yin and his team's experiment.

The current version is the final version that Chang Yin and Xue Lan debugged through various experiments. The initial effect was very weak, and the bats in the staircase passage were the initial test subjects.

After consuming the initial experimental drug, the bats did mutate and gained certain special abilities, but the abilities of each individual bat were too weak, and they had to work together in groups for their abilities to manifest.

Xu Xin had suffered a loss at the hands of a swarm of hundreds of bats. Recalling the feeling at that time, his head even started to ache again.

"The power of a bat swarm is ultrasonic waves that can affect people's minds." Xue Lan was also very familiar with the test subjects and explained to Xu Xin, "But a single bat is useless. It's just a little bigger than an ordinary bat and has a slightly longer lifespan."

Before Xu Xin could say anything else, the bat that had flown into the cave above flapped its wings and flew down, holding a red stone the size of a walnut in its claws.

"Look, doesn't this still have some effect?" Xu Xin reached out to catch the small round red stone, and when he focused his eyes, he found that the stone actually emitted a blue light.

It's actually a blue-grade stone.

When Xu Xin saw the word "radiation", he almost threw the stone away, but he felt relieved after reading the introduction below.

Xu Xin couldn't help but smile after understanding the stone's function. It turned out to be a tool that could make mutant beasts stronger! This was simply what he wanted.

The mutant cheetah is currently on the edge of low-level and mid-level. As long as it can become a little stronger, it can be directly upgraded to a mid-level beast! And the stronger bat can also play a greater role.

I didn’t expect to find such an unexpected surprise here.

"What? Is this stone useful?" Chang Yin asked, looking at the stone in Xu Xin's hand.

"It's nothing, just a piece of stone that can be used to make weapons." Xu Xin put the stone into his backpack.

"Weapons? That's boring. My body is the weapon. Okay, push the door." Changyin pointed to the door in front.

Xu Xin walked to the door and reached out to touch it.

"Huh?" A familiar feeling rose from the bottom of my heart. This feeling is... a tree house?

It was like pulling at the roots of the tree house, feeling as if it had become one with me. Could it be that the roots of the tree house were affecting the door here?

With a gentle push, the huge double door slowly opened inward. Xu Xin quickly hid to the side, fearing that something might come out of the door.

Behind the door was still a spacious corridor like a tunnel. Unlike the previous section of road, the ground in front was paved with alternating black and white bricks. Each brick was a square with a side length of about one meter. The entire road appeared to be covered with black and white grids.

"Trap?" Xu Xin expressed his guess.

"That's right." Chang Yin pointed to the two colored grids on the ground. "Every grid could be a trap, but it could also be safe."

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