“They aren’t a specific species. They can range from Twin-Armed Monkeys to even rare species from the 6th Floor. The only thing differentiating them from ordinary creatures is the strange mark they have on their bodies,” Lee Jun-Young explained.

“By a strange mark, you mean...” Kim Jin-Woo began.

“They have something like a tattoo on them, in the shape of a half-opened eye. And the creatures that bear this mark are what we call ‘Sentinels’.” Lee Jun-Young went on to explain how these 

Sentinel

 beings had brought death and destruction upon the human army in the previous war, before concluding, “It seems the institute isn’t going to let this matter rest this time. The moment the Sentinels made their appearance, peace was no longer an option.”

“But come to think of it, weren’t the humans the one to break the armistice first? Isn’t a massive invasion into the Underworld an act of aggression in itself?” Kim Jin-Woo suddenly noticed that he was rebuking the humans, and quickly stopped himself from saying anything further.

But thankfully, Lee Jun-Young didn’t seem to notice anything. She replied, “That may be true, but the government is worried that the Sentinels may rise up to the surface just like before. People are still speaking as though another war is out of the question, but I disagree, just from the way things are moving.”

Having roughly gauged the developments on the surface, Kim Jin-Woo let out a deep sigh.

“Jin-Woo, please take care.”

“You too, Jun-Young.” Kim Jin-Woo said goodbye in response to Lee Jun-Young’s anxious farewell as he headed to Mr. Baek’s appraisal office.

“A war seems imminent. I can’t believe those awful things have shown their faces once more,” Mr. Baek remarked.

Neither Lee Jun-Young, Mr. Baek, nor anyone else Kim Jin-Woo encountered highlighted the fact that it was the Terrans who had invaded the Underworld first.

Kim Jin-Woo felt disgusted at this hypocrisy, but didn’t let it show. He left Mr. Baek’s appraisal office and returned to the Underworld, right as the Black Merchant coincidentally visited him again.

“Since the situation on the 5th and 6th Floor have roughly wrapped up, it’s time for us to start making our move.”

While the Terrans saw the situation in the Underworld as chaos unfolding, the Underworld saw it as stability being restored. Kim Jin-Woo felt head-splitting pain from constantly traveling between the surface and the Underworld, and simply 

listened

 to what the Black Merchant had to say.

“We plan to leave in three days, so please make your preparations accordingly. I’ll see you again then.” As he finished what he had to say, the Black Merchant then prepared to leave the labyrinth. He didn’t mention the Guardians at all, as if he had anticipated this outcome from the beginning.

“The surface is prepared for a war,” Kim Jin-Woo told the Black Merchant as he started walking away.

However, the Black Merchant didn’t even bat an eyelid as he responded, “A war?”

“They have very strong feelings toward the Guardians. In the worst case, they’re ready to go to war.”

But the Black Merchant seemed unfazed. “There won’t be another large-scale war like the previous one.”

“And how are you so sure?” Kim Jin-Woo almost nodded in agreement due to how confident the Black Merchant sounded, but he questioned the source of the Black Merchant’s confidence.

There was a brief moment of silence before the Black Merchant replied, “The Terrans who remember the day of the armistice would never dare to set foot into the Underworld once more.”

As Kim Jin-Woo pondered the Black Merchant’s words, the latter started to make his way back once more.

“What exactly happened that day?”

Unable to get a clear answer, Kim Jin-Woo let the Black Merchant go as he stared long and hard into the empty darkness of the Underworld, lost in thought, wondering about the day of the armistice.

***

[The labyrinth’s upgrade is complete. The labyrinth has been upgraded from Level 1 to Level 2. Previously locked facilities are now accessible.]

[You may now summon Wraith Workers through the Altar of Wraiths.]

Upgrading the Labyrinth of Mirror Wraiths was proceeding smoothly.

There was no further need for Kim Jin-Woo to worry about lacking funds to upgrade his labyrinths, nor did he need to worry about them being exposed to attacks. Thus, it was a given that the Labyrinth of Mirror Wraiths would upgrade rapidly as planned.

[The labyrinth’s upgrade is complete. The labyrinth has been upgraded from Level 2 to Level 3. Previously locked facilities are now accessible.]

In a short amount of time, the labyrinth had been upgraded twice and was now at Level 3.

“Hm, do I have to wait and see a bit longer?”

He had yet to notice a significant difference from the base level of the labyrinth. The only difference was the on-off presence of the Wraith Workers, which he found to be a bit odd. Aside from that, the Labyrinth of Mirror Wraiths felt no different from any other labyrinth.

It was almost as if the 

Silk Frogs’ nest 

was more useful. The nest had been upgraded to Level 3, and while the Pentacolored Frog Warriors weren’t too competent in combat, what they lacked in strength, they made up with their special ability to paralyze their foes with poison.

Kim Jin-Woo had tested out the capabilities of their poison on the Naga Warriors as well as the Tiger Dragons, and had seen them become instantly paralyzed. That had convinced him that the Silk Frogs were, in fact, more useful than he had initially thought.

But in contrast to them, the Big-Headed Dwarves were truly utter rubbish. Even their workers had massive heads and relatively short arms and legs, which severely hindered their ability to carry out tasks in the labyrinth. The subsequent summons proved to be no better.

However, this dynamic changed completely when the Labyrinth of Mirror Wraiths was upgraded to Level 4.

When the labyrinth, which was eventually dubbed the Pool of Mirror Wraiths, was upgraded to Level 4, a frightening amount of changes occurred.

The most unusual thing, however, was that there were only two available summons after it reached Level 4. Other than the Wraith Workers, there had previously been no other summons available, which caught Kim Jin-Woo off-guard.

To test this out, Kim Jin-Woo threw a creature he had captured from the 9th Floor into the middle of the pack of Wraiths, and it wasn’t long before one of the Wraiths took on the exact form of that very creature.

As Kim Jin-Woo looked on in awe, he finally understood the true worth and power of these Mirror Wraiths. As long as he could find beings to extract abilities from, these Wraiths would continue evolving without end.

Of course, the drawback was that until he could find such sacrifices, these Mirror Wraiths were no different from the Wraith Workers in terms of usefulness.

“Still, this is pretty fucking amazing.”

Despite the Mirror Wraiths not being able to absorb beings beyond their own level, Kim Jin-Woo was more than satisfied with the outcome.

“Croak!”

However, the Silk Frogs remained pretty much the same. He had been hoping that they would get better as their labyrinth upgraded, but the Pentacolored Frog Warriors remained as they were with their paralyzing poison ability.

Perhaps they required even more upgrades before he could come to a conclusion in terms of their potential.

And as expected, the Big-Headed Dwarves were completely useless. Thus, he decided to stop upgrading their labyrinth and extract its core for another purpose.

“Such a shame that it’s come to this.”

He felt conflicted, as he knew that the core in his hands was home to the only Big-Headed Dwarves in the Underworld. Using the core for synthesis would mean the end of the Big-Headed Dwarves as a species.

He thought long and hard before finally deciding on using the core as a test subject for experimentation. The advanced Naga Sorcerers were undoubtedly excited at the prospect of a new experiment.

[The 

Heart of the Big-Headed Dwarves

 is being enhanced.]

[You require a Labyrinth Fragment.]

[Would you like to use the Fragments of the Abandoned Labyrinth for the enhancement?]

“Yes.”

Kim Jin-Woo had decided to wipe out the Big-Headed Dwarves from existence should the enhancement bring no significant change.

[The Heart of the Big-Headed Dwarves has been enhanced.]

“What? That’s it!?”

There were no further explanations. A short flash of light and a single message was all that appeared at the end of the enhancement.

The only significant difference was that the highest-grade down gem that contained the core of the Big-Headed Dwarves’ labyrinth was emitting a faint and colorless shade of light.

It seemed as if the enhancement wasn’t entirely fruitless.

“No, stop!”

In the brief moment when Kim Jin-Woo turned his attention away, the advanced Naga Sorcerers had begun attempting to enhance the core once more, and he quickly ordered them to stop.

Should the enhancement not bring any useful results, he would have to remain awkwardly in possession of this questionable Labyrinth Core.

Even if the result of the enhancement turned out to be more useful than he could imagine, it was still for the better that he enhanced other cores that he knew for certain could bring better results.

Belatedly realizing this point, he took back the Labyrinth Cores and fragments that lay on the table of the research lab. The Naga Sorcerers stood by him as they watched on with disappointment.

“I mean, if you had something like this in your possession, you should have told me about it earlier!”

Unexpectedly, it was the Black Merchant who helped to take care of the Big-Headed Dwarves’ core.

Kim Jin-Woo figured that the Black Merchant would prize any labyrinths, no matter how useless they seemed, and he was right.

“I’m telling you, they’re truly garbage. With their stumpy arms and legs and oversized heads, there’s nothing they can do.” Kim Jin-Woo spoke truthfully, as there was no benefit in him trying to oversell the burdensome core. However, the Black Merchant was still visibly displeased.

“Ah…”

In hindsight, Kim Jin-Woo realized that the Black Merchant looked similar to the Big-Headed Dwarves. Aside from his red skin and pointy ears, he seemed no different in appearance when compared to the Big-Headed Dwarves or the imps.

Kim Jin-Woo realized that he had indirectly attacked the Black Merchant, who himself had short arms and legs and a big head.

“There is no such thing as a useless species.” Having said that, the Black Merchant seemed to calm down. “You should know that the creation of a new species is far rarer than the extinction of an old one in the Underworld, right? The birth of a new species is in itself a beautiful thing to behold.”

It was in such moments that Kim Jin-Woo felt that there was more to the Black Merchants than met the eye. Otherwise, there was no reason for a group of profit-driven merchants to feel so protective about all the beings of the Underworld.

As Kim Jin-Woo stared at the Black Merchant, the latter coughed lightly to break the silence that followed, saying, “If you happen to be caught in such a situation again, please let me know and I’ll be here immediately.”

Kim Jin-Woo had been worried that the Black Merchant might start nagging again, but thankfully, he didn’t seem to be aware of Kim Jin-Woo’s experiments with the core synthesis.

The Black Merchant held tightly onto the Labyrinth Core that was handed to him as he began to move out of the Fortress.

***

After the departure of the Black Merchant, Kim Jin-Woo fell into deep thought as he wondered how to best utilize the Mirror Wraiths.

He knew he could create a formidable army should he have the right resources, but with no immediate resources available, he was feeling frustrated.

“Ah!”

He abruptly stood up, having remembered the countless corpses that Valicius had surrendered to him in their previous battle.