Several hours had passed since Byune began advancing through the cavern, discovering and disarming traps along the way. Throughout that time, she had worked without her concentration ever wavering — but by the time they reached the end of the passage, she was understandably exhausted.
If Rei and his party had been an ordinary group, it would not have been unreasonable for them to call it a day and set up camp right there.
Whether fortunate or not, there were no hostile monsters lurking in this hidden cavern.
In other words, safety was not a concern when it came to making camp.
Of course, whether anyone would actually want to camp in a cavern riddled with traps was another matter entirely.
Regardless, Rei and his party showed no such hesitation and began exploring the area where the passage opened up.
But that was only natural. After descending the stairs in the forest, they had found themselves in a space carved out of solid rock. After clearing out the Rock Plants there — though since those were not technically monsters, "defeating" may not have been the right word — they discovered a hidden door and proceeded through the cavern beyond it.
They had no idea what the intention behind all of it was, but they pressed onward, disarming the countless traps that had been laid along the way... until the place they finally arrived at opened up into what could only be described as an underground lake.
"The water is glowing because of the moss growing in it. I've never seen this type before, either."
Marina murmured as she gazed into the underground lake.
Just as she said, the lake was filled with red, blue, yellow, green — a whole spectrum of light, as if it were some kind of illumination display.
It was a far cry from the image that the words "underground lake" would typically conjure up.
However, the moss glowing in the water and clinging to the cavern walls serving as a light source was a stroke of good fortune for Rei and his party as well.
If not for the moss, this place would likely have been swallowed in total darkness.
In that sense, the colorful moss in the water was undoubtedly something to be grateful for.
"Even though this connects from that cavern earlier, the rocks here don't glow or anything... I don't have that much experience diving into dungeons, so I wouldn't know. Is every dungeon like this?"
Rei shook his head at Reliu, who asked while gazing out over the considerably large underground lake.
"Every dungeon is vastly different from the next. There are places like this, and places that aren't. As far as I know, there's never been a dungeon with no light source at all, so you don't need to worry about that."
"...That's awfully convenient."
"I can't say I disagree, but ask the dungeon core if you want a detailed explanation. I wouldn't know even if you asked me."
That was how Rei answered Reliu — though in reality, he had destroyed dungeon cores several times already by means of Death Scythe.
As a result, Death Scythe had even acquired the Terrain Manipulation skill.
It was an impossible notion, but if Reliu had known about those circumstances, he certainly would have called Rei out on it.
"Putting that aside... is this underground lake a dead end after all? If so, I think we need to figure out what to do from here."
Vihera murmured as she surveyed the area around the underground lake.
Indeed, just as she said — having come all this way, if it turned out to be a dead end, then the only option would be to turn back.
Of course, this underground lake most likely held some kind of significance.
Even so, given their current situation, nothing here suggested there was anything of note.
"If we're going to investigate, it would have to be that underground lake."
In response to Vihera, Elena murmured while gazing out at the underground lake, awash in its myriad of lights.
At the end of Elena's gaze, Rei had spotted the silhouette of a fish in the lake that he had never seen before.
"Huh, so there are fish even in an underground lake like this. Think they're edible?"
For Rei, fish evidently still registered first and foremost as food.
The reason he did not declare them edible outright, however, was likely because this was an underground lake.
If this had been a river, the sea, a swamp, a pond — or even a lake, as long as it was an ordinary one on the surface — he probably would have said so with confidence.
(Well, I don't think they're inedible... but there's no denying they didn't exactly look appetizing.)
It was only for a brief moment, but the fish Rei had glimpsed appeared to be scaleless, with a somewhat curvilinear body — much like a catfish, an eel, or a conger eel.
Of course, all of those fish were quite delicious.
But just because it resembled them did not necessarily mean the fish in this underground lake would taste good... honestly, Rei could not say with any certainty.
"Rei? What is it?"
"Nah, it's just this underground lake. Looks like there are fish in it. I was just wondering whether they'd be any good to eat."
Marina cast a slightly exasperated glance his way, as if to say this was hardly the time to be thinking about such things.
After all, a fair amount of time had already passed since they descended the stairs in the forest.
In other words, if they were to head back from here, it would naturally take a proportionate amount of time.
Of course, since Byune had already disarmed every trap in the cavern on the way in, the return trip should not take nearly as long.
"Hmm. I have my doubts about Rei's line of thinking, but given that there is an underground lake like this here, there is almost certainly something to it. That is what I think, at any rate. What about you?"
Elena murmured while scanning her surroundings for anything suspicious.
It was true — the cavern leading to this underground lake had been concealed behind a hidden door.
Given that, there had to be some kind of secret to this underground lake.
The question was what kind of secret... that was the real issue.
"Since there's an underground lake right here in plain sight, it's a safe bet that there's something in the lake."
"Indeed. Otherwise, there'd be no reason to deliberately hide the path leading here."
Marina murmured, turning her gaze toward the underground lake.
The look in her eyes was no longer that of someone enjoying the underwater light show as before. It was the gaze of someone calculating what lay here and how to unravel the mystery before them.
"To begin with, this is the first underground lake I've ever seen... is one this size normal?"
Rei murmured as he looked out over the vast expanse of water before them.
The underground lake stretching out before his eyes was quite large.
(If this were Japan, would people describe it as the size of one Tokyo Dome? ...I have no idea why Tokyo Dome became the standard for measuring area. I've never even been to Tokyo Dome, so I don't know how big it actually is — I can't even be sure if "one dome's worth" is the right way to describe it.)
Rei's thoughts drifted to Tokyo Dome... but then he caught sight of ripples forming on the surface of the water, roughly in the middle of the lake.
Naturally, he was not the only one who noticed — everyone's gaze snapped toward the water.
And then, as if breaking through the surface, a creature... or perhaps a monster, made its appearance.
However, looking at the part that was extending above the water — that long, slender portion — there was no telling how much of its body still lay submerged.
"A snake?"
Who was it that murmured that?
Indeed, going by the portion above the water alone, it had a form befitting the name.
...Of course, considering that the part visible above the surface alone must have been about five meters in length, it would be hard to compare this snake with an ordinary one — the kind you might commonly see outside.
And beneath the water, a long body was visible enough to make one recoil at a glance.
The snake's throat appeared to be moving, perhaps because it had swallowed a fish or something similar.
That much Rei could not say for certain, but what he could say without a doubt was...
"Strong, huh."
Reliu muttered beside him.
Yes — the strength Rei had sensed from that snake, Reliu had felt it too.
No, it was not just Reliu.
Everyone present — even Byune, who fell a step or more behind the others in terms of pure combat technique — could feel the snake's strength radiating from where it surfaced.
"What do you think?"
What came from Rei's mouth was a brief question, but it was enough to convey his meaning to everyone there.
"A Boss Monster... isn't it? Looking at it like this, it seems to possess considerable strength."
"I understand why you'd say that, but then where's the dungeon core? ...At the bottom of the lake?"
"Compared to the Silver Lion, it still seems like we might manage."
Whether she was listening to Rei's words or not, Elena murmured while recalling the strength of the Silver Lion she had once fought.
The Silver Lion she had fought to save Vihera.
Its strength had been intense enough to deserve the label of an S-Rank monster.
Set, who wielded a variety of skills and was treated as an S-Rank-equivalent monster due to being a Rare Species, would almost certainly lose to the Silver Lion in a one-on-one fight — that much was easy to predict.
That was the kind of power the Silver Lion possessed.
Compared to a creature like that, the giant snake currently surfacing from the underground lake was undoubtedly a formidable foe, but it was hard to believe it was stronger than the Silver Lion.
That was why Elena, even looking at the snake, felt it was strong but did not feel the despair of facing an unbeatable opponent.
(Though of course, that snake is in an underground lake. Unlike the Silver Lion, we'd need to draw it out of the water.)
Just recently, during their trip to the sea, Elena had watched Rei struggle against a monster in the ocean.
This despite the fact that if they had fought normally, the difference in their abilities was such that Rei would have won overwhelmingly.
...Of course, Rei had been fighting the monster for food, so he could not simply blow it to pieces — he had needed to defeat it in a way that left it properly edible.
Additionally, Elena herself recalled struggling considerably when she had fought a Kraken in the past, so she understood all too well that fighting an opponent in the water was extremely difficult.
"What do we do? Fight? You want to fight, right?"
While everyone was struck silent by the snake's sheer presence, the first to speak was, as expected, Vihera.
For someone like Vihera, who relished battles against powerful foes, being told to suppress her combat instinct in the face of that giant snake — clearly a formidable creature at a glance — would have been an impossible demand.
Moreover, Vihera had not taken part in the battle against the Silver Lion either, which only made her hungrier for combat against a powerful monster.
Her attitude made it perfectly clear — there was no way she was going to let such a golden opportunity slip through her fingers.
However... there were those who voiced opposition to Vihera's words.
"Do we really need to fight? It hasn't made a move against us so far. I don't think we need to force a battle here."
The one who said that was Reliu.
For Reliu, who had come along as reinforcements for Rei's party, fighting some weak monster like a Goblin that could be found anywhere was one thing — but going up against a strong enemy like the snake in this lake was something he absolutely wanted no part of.
In the first place, this dungeon was newly formed. The boss guarding the dungeon core should have been a fairly weak monster... or so it should have been.
But upon actually entering the dungeon, the first floor had been more or less what they expected — just a single Y-Fork — and had been a predictable enough dungeon (though the inexplicable presence of Rock Plants was certainly unusual). Once they ascended to the second floor, however, they found a vast forest stretching out before them.
It was nothing that could pass for a newly formed dungeon.
And after descending the stairs in that forest, they had found an enormous space filled with the same Rock Plants that had appeared on the first floor... and ultimately, they had arrived here, at this underground lake.
The giant snake now looming before Reliu and the others was not the kind of creature that should appear in a newly formed dungeon.
It seemed to possess enough power that Reliu would need to fight all-out just to have a chance of winning — that was the impression it gave off.
That was why he had suggested there was no need to force a fight against such an opponent... but unfortunately, that kind of reasoning did not work on Rei and his party.
Vihera welcomed a battle against a strong enemy, and more importantly, Rei absolutely wanted the magic stone of an unknown monster.
Since it would enhance his Beast Magic, there was no such thing as having too many magic stones from unknown monsters.
And above all else...
"Look, Reliu."
With that, Rei pointed toward the bottom of the underground lake.
Under normal circumstances, it would have been impossible to see the bottom of such a deep body of water — but this lake was filled with moss glowing everywhere like an illumination display.
And perhaps the water itself was not ordinary... for even the depths of this considerably deep underground lake were clearly visible.
Yes — even what appeared to be the dungeon core resting at the very bottom.