When Ning Fan understood this, he could basically guess what would happen next.

This technology became increasingly out of control, and eventually, all the members of the Li family became bloodthirsty and began using the strongest members of their own branches to cultivate new types of exotic beasts.

until……

Completely out of control!

No matter how powerful a group is, its former glory will be lost in this endless internal friction and almost crazy killing.

When these powerful Li family members in the world of swords were left on the battlefield, the structure of that world finally collapsed.

The Li family's self-weakening gave other families an opportunity to reshuffle.

Ironically, it was only after the strange beast developed its own thinking that the Li family finally woke up.

They realized that they seemed to have become sinners.

The reason why every remaining soul in the world of the sword chose to rename themselves "Wu" is precisely because they did not want to admit that they were members of the Li family.

On the one hand, they feel that they are not worthy of enjoying the surname left by their ancestors.

On the other hand, he also didn't want to bring shame to the Li family.

After listening to Xin Wuluan's story, Ning Fan was silent for a long time.

He couldn't even imagine how crazy that period of history was.

Compared to the situation back then, Ning Fan didn't even think the current Lower City could be called hell.

Then, Ning Fan recalled the dream again.

That should be the beginning of this battlefield becoming the lower city.

Those who woke up realized that the strange beast had grown to a point where they could no longer control it.

And in the upper city, there are their relatives.

They were the ones who created the strange beasts, so they knew better than anyone that if they let them go to the upper city, then...

There will inevitably be great suffering above.

Since they were the ones who caused the disaster, it is up to them to put an end to it all.

At this moment, the Li family finally showed their "character" and "magnanimity".

They used their lives to seal the entrance to the battlefield.

At the same time, they also gave this if a name.

[Prison Gate].

From this moment on, the two worlds were completely isolated.

However, those on the battlefield did not think that everything would end like this.

At that time, there were seven people who were recognized as the most powerful in their respective fields, and they also merged with strange beasts.

To be frank, their thoughts at that time were ridiculous.

The reason they were willing to become alien beasts...

He just wanted to stand up for his own bloodline.

Reason was too luxurious in the crazy context of that time.

After they merged into strange beasts, they became so powerful that they were almost invincible.

They knew that this [prison gate] might not be able to keep "themselves" on the battlefield forever.

so……

They were imprisoned.

They left most of their abilities in their residual souls.

The container that imprisoned their remaining souls became the [Key].

Ning Fan finally understood the true function of the [Key].

It's not about opening the [prison door], nor is it about liberating the fifth-level beast.

It is the key to liberating these remaining souls.

Perhaps, as time goes by, the role of the key has changed in the communication between people.

The [key] can indeed open the [prison door].

Because, while these residual souls still exist, the fifth-level monsters may still "steal" their abilities.

But when these residual souls were completely freed, the so-called fifth-level beasts were left with only a once-powerful shell.

They will not be a threat.

People in the lower city can also stand in front of the [prison gate].

"You guessed one thing right."

After Xin Wuluan had spoken out everything, he felt noticeably relieved: "Higher-level exotic beasts, their weakness is their reproductive ability."

Ning Fan's eyes fixed.

Now, everything Xin Wuluan said was the key point for him to go to the upper city.

The weakness of higher-level beasts is their reproductive ability, and fifth-level beasts will become useless as their residual souls disappear. In other words...

Ning Fan now basically has the strength to kill.

"The so-called high-level exotic beasts are nothing more than the best ones back then."

"After transforming into strange beasts, their lives are also extended indefinitely."

"That's why many people chose to convert at that time."

"However, when you gain something, you will inevitably lose something."

"What they lose is their normal reproductive ability."

"On the contrary, those low-level exotic beasts are easier to give birth to."

Ning Fan couldn't help but feel a little frightened when he heard this.

He thought of a question.

This [top wall] has existed for at least hundreds of years.

Let's not even talk about how long those high-level beasts have existed, just look at their numbers...

Humans have been fighting against alien beasts for hundreds of years, but they haven't killed them all yet...

How many extraordinary geniuses did the Li family transform back then?!

The truth was far crazier than Ning Fan had just imagined.

In fact, there is another question that Ning Fan can't figure out.

But it's a little difficult to speak.

Xin Wuluan seemed to see what Ning Fan was thinking, so he asked, "Are you curious? If you really wanted to seal this place, why did you leave a [Key] behind?"

"No, to put it more directly, why didn't you just kill us all at the beginning? Why did you leave behind some of our souls?"

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