An icy chill continued to spread from the narrow cave.

If he wants to enter this cave to explore, he may not be able to explore comfortably with his current equipment.

Just the chill radiating from the cave could make Xu Xin shiver standing at the entrance of the cave. The temperature inside must have been below minus 50 degrees, or even much below zero.

He looked at the time and saw that it had only been more than half an hour since he climbed up. There was still plenty of time left before the twelve-hour deadline given to him by the mission.

And he has climbed more than three hundred meters.

It's not surprising, because this twelve-hour time limit is prepared for ordinary survivors. But today, his arm strength has increased, and his climbing speed is much faster than ordinary survivors.

He used enough time to stop, rest and explore during the climb.

"Click..." There was another subtle sound.

This time, because she was at the entrance of the cave and the sound came from inside the cave, Xu Xin heard it clearly.

It sounded a bit like the sound of something cracking.

For example, the sound of rocks cracking or ice breaking.

Xu Xin looked at the corner at the end of the cave and decided to go in and find out.

He did not take out the energy core fragments directly, but walked in slowly.

If there is any danger inside, the light from the energy core fragments may disturb it.

In this cold high altitude, he couldn't help but be careless, so he could only walk quietly into the cave by himself.

Step by step, he walked gently to the corner of the cave.

Although they had just separated not long ago, Xu Xin already missed Coco a little.

If it was Coco, he should have been told by now whether there was any danger in the cave.

If there was no danger, the little guy Ke Ke would probably jump off his shoulders and rush in before him.

Of course, Cocoa can't stand such low temperatures at all.

Taking a gentle breath, the icy chill penetrated directly into his heart and lungs.

The surrounding temperature was already below minus 50 degrees, and he could already feel the obvious coldness, which was roughly equivalent to the feeling of going out in short-sleeved clothes in the winter.

However, because his current physique is already unusual, he can still bear this kind of cold as long as it doesn't last too long.

He took out a blue-level iron sword from his backpack. Yes, it was the iron sword made for cave use when exploring the dungeon.

The cave this time was also very narrow. Of course, it was much wider than the maze cave that time. That time I could only pass sideways, but this time I could at least walk normally.

Turning the corner, there is a straight and narrow passage.

This straight and narrow passage, less than one meter wide, is different from the cave outside the corner. The rock walls are relatively neat, and it looks a bit like an artificial passage.

There is a thin layer of frost on the stone wall of the passage.

A strange feeling arose in Xu Xin's heart. He always felt that there was something inexplicably familiar here.

"Click..."

The slight sound came from the end of the passage. He quickened his pace and walked forward quickly without making any noise.

Soon, he came to the end of the passage.

"This is……?"

The extremely biting chill could not conceal his surprise at this moment.

At the end of the passage, there is a door!

A... somewhat rotten wooden door!

The entire door is very decayed and even tilted. The entire facade is very tattered and has some cracks. There is a thin layer of frost on the wooden door.

This door looks like it will fall down if pushed.

This wooden door looks so familiar!

The material, the degree of decay, and the familiar door handle style...

Aren't these the rotten wooden doors of the rooms in the underground city where he found Chang Yin's family?

This...why is there such a wooden door here?!

and……

He turned around and looked.

The familiarity he felt as he walked through this passage gradually fermented, and memories began to emerge in his mind.

It’s the stone wall of the underground city passage!

The stone wall of this straight passage is exactly the same as the stone wall of the underground city, made of exactly the same material!

However, even the narrowest place in the underground city's passage is much wider than here. Moreover, various decayed wooden doors are on both sides of the passage. The door here is only the one at the end of the passage, so

He didn't recognize it immediately.

Underground city...? In this giant peak, high in the sky, is there an underground city?

"Click..."

Another sound came from behind the almost completely decayed door and from inside the room.

The thing that makes the noise is inside.

So weird!

Xu Xin could feel that because of the low temperature, the air here was very dry, so the air humidity was also very low.

If he takes a deep breath, he will not only tremble with cold, but also have a dry mouth.

If this door had been kept in such a low temperature and dry environment, it would be impossible for it to decay like this!

The wooden doors of the underground city were rotten because the environment was very humid, so humid that water droplets would drip from the rock walls above.

The door here shouldn't be...

Looking at the frost on the wooden door, it gave him the feeling that... the originally humid and warm environment suddenly became very cold, and then the moisture was frozen directly on the door. It looked like

It's like the door is sealed with ice.

...Yes, didn’t this mountain peak appear suddenly?

In one night, it rose from the ground and suddenly appeared.

Wait... rise from the ground?

Xu Xin seemed to understand something.

Could it be that...this place is originally an underground city?

However, because the entire stone pillar peak rises from the ground, part of this underground city is brought out?

...Yes, that should be correct.

This can also explain why the environment here suddenly changed.

I really didn't expect that he could actually explore the underground city on the snowy peak at an altitude of more than 300 meters.

After standing motionless for a long time, Xu Xin felt like she was going to freeze due to the low temperature here.

He buried his head in the snow fox scarf, took a breath, and then stretched out his hand to push towards the frozen door in front of him.

At this time, the door was completely frozen and could not be easily pushed open.

Helpless, Xu Xin could only increase her efforts.

"Click!" The door was not pushed open, but pushed down.

This kind of rotten wooden door could not withstand the current low temperature and freezing conditions, so he not only pushed the ice away, but also deduced the hinge of the door, causing the entire door to fall backwards.

"Snapped!"

Although the door has rotted away, it was solidly frozen. It made a sound of ice hitting the ground when it was thrown to the ground. It was not broken at all and was still intact.

Xu Xin also looked into the room.

The room is not big, and is basically the same size as those in the dungeon. After all, this is a room in the dungeon.

"This is..." With a look on his face, he immediately stepped on the door that was pushed to the ground and stepped into the room.

In the middle of the room, there is a strange-looking device.

The lower part of the device is made of iron and is already stained with red rust, while the upper part is made of glass. The overall shape is square. At first glance, you might think it is a strange fish tank.

However, under the sudden change in temperature, the entire device seemed to be frozen, and the glass was covered with frost and cracks. It was like one side of tempered glass that had been broken, full of cracks but still stuck together, completely invisible.

the things inside.

Xu Xin could hear rustling sounds coming from inside, and... weak breathing?

Um?!

Is there anything alive in here?!
To be continued...