Rei had been investigating the Wisp alongside Anastasia in the Underground Space, but with plenty of other tasks demanding his attention, he eventually took his leave.
He was still worried that her intense curiosity might drive her to do something strange to the Wisp. However, Anastasia had promised to exercise self-restraint for at least a few days, and he took her at her word.
...Though that didn't mean he was truly reassured.
With so much on his plate, though, there was nothing he could do about it.
"In that sense, an assistant really is necessary. ...I just hope she doesn't pick some oddball."
"Gruu?"
Hearing Rei's muttered soliloquy from atop his back, Set—currently navigating through the Treant Forest—turned his head as if to ask what was wrong.
The fact that his speed never dropped even while turning around, weaving between the trees of the forest, was a testament to Set's exceptional abilities. Though for Set himself, something of that level probably didn't even warrant conscious thought.
"No, it's nothing. I was just thinking this whole affair is shaping up to be quite troublesome."
"Gurururu."
Set purred in response, as if unsure how to reply.
Rei stroked him as they continued through the Treant Forest, but Set—who had been happily leaning into the neck scratches—suddenly snapped his gaze forward.
"Gruu!"
Set let out a sharp cry, staring ahead.
A few moments behind Set's reaction, Rei also fixed a sharp gaze forward. He sensed that a battle was underway not far from their position.
Without a word, Rei gave Set's back a light tap. That alone was enough for Set to understand; he broke into a sprint, noticeably faster than before.
His figure darting between the trees of the Treant Forest—if an ordinary person had caught a glimpse, they might well have perceived it as nothing more than a brief flash of a black shadow.
Running at such speed among so many trees would normally be sheer suicide. But for Set, it was as if such concerns were irrelevant. He ran and ran and ran through the forest.
When undergrowth blocked his path, he smashed right through it. When vines hung between trees, he charged in without a care, tearing them apart.
After about twenty seconds of running, he burst through the thicket directly ahead—and they arrived at the battlefield.
Before them unfolded a scene of adventurers locked in combat with a horse monster whose body was made entirely of grass.
The presence of woodcutters behind the adventurers made it immediately clear that, unlike the adventurers who had previously wandered into the Treant Forest while fleeing from Cobolts, these were men who had accepted a Guild request to escort woodcutters. Above all, Rei recognized many of the adventurers fighting there.
Given that, the option to not join the battle didn't exist for Rei.
...Though truth be told, the very existence of an unknown monster like a horse made of grass meant there had never been any such option to begin with.
"Providing support!"
Leaping from Set's back as the creature charged toward the grass horse, Rei drew Death Scythe and the Twilight Spear from his Misty Ring.
From watching the grass horse fight the adventurers, he could tell this area was fairly open—with enough room to swing long weapons.
"Gururururuu!"
Set barreled in and delivered a strike with his front leg.
This was no ordinary blow; it was his Power Crush skill. Set possessed numerous skills, but Power Crush was at Level 6—the highest among all of them.
The strike landed squarely on the grass-constructed horse. In the next instant, its body burst apart, scattering grass across the surrounding area.
"Gruu!?"
Set let out a bewildered cry. The blow had indeed connected, but the resistance had been overwhelmingly less than what he'd anticipated. His demeanor betrayed the question forming in his mind: Why?
Rei, for his part, was relieved that the creature had been taken down—but then...
"It's still alive! That thing's still alive!" one of the adventurers shouted sharply.
Though slightly smaller than Set, the grass horse stood over two and a half meters tall. More than half its body had been effortlessly shattered by Set's Power Crush, and Rei had naturally assumed it was dead. So when the grass scattered across the ground began moving as if alive, crawling toward the half-destroyed horse, his face twisted.
"Multi Slash!"
Left as it was, the grass creeping along the ground would heal—no, regenerate—the creature.
Rei's response to that judgment was Multi Slash. The skill allowed multiple slashes to be unleashed in a single strike, and Rei's Multi Slash was currently at Level 3. That meant three additional slashes would be delivered on top of the one he swung with Death Scythe.
What's more, the weapon he'd activated the skill through was Death Scythe, whose blade was roughly a meter long. With three extra slashes layered on top, the grass horse—already reduced to half a body—was effortlessly shredded.
Just as with Set's Power Crush, its body scattered, sending grass flying across the area.
It scattered, but...
"Huh? There's no... Magic Stone?"
The grass horse's body had already completely collapsed, yet the Magic Stone that any monster should possess was nowhere to be found.
The thought crossed his mind that perhaps Multi Slash had destroyed the Magic Stone and sent it flying—but if that were the case, there should have been some sensation of slicing or shattering it lingering in his hand.
Naturally, no such sensation existed.
In other words, the grass horse hadn't possessed a Magic Stone.
...At least, assuming one hadn't simply rolled across the ground or flown off somewhere without him noticing.
"Huh? This monster... no Magic Stone, does that mean—"
Rei cut his words off there.
He was familiar with one exceedingly rare category of creature: monsters that possessed no Magic Stone.
The lake from another world, teleported in by the Wisp. He had fought the monsters inhabiting that lake, and none of them had yielded Magic Stones.
The Water Strider, the lizards, the giant fanged fish. Within the corpses of all three types, no Magic Stone had existed.
Granted, leaving aside the latter two, the Water Strider's head had been blown apart into the lake by Set's diving attack from above, so the possibility that its Magic Stone had been inside its head couldn't be entirely ruled out.
Still, as far as Rei knew, the only monsters without Magic Stones were the ones from that lake.
(Which means... did this monster come from the lake too? Now that it's mentioned, the grass making up its body doesn't look like the kind that grows in the forest—it does seem more like some kind of aquatic plant.)
If so, the question was where it had come from. The only place near the lake with guards like Rei's group was beside the Birth Tower. And the lake itself was roughly as vast as Gilm.
In other words, even if a monster from the lake came ashore, it wouldn't be discovered unless it surfaced near the Birth Tower.
This grass horse—could it be one such creature that had emerged from the lake?
That was Rei's conjecture.
...The absence of a Magic Stone alone all but confirmed it.
That said, he couldn't entirely dismiss the possibility that this wasn't the main body—that some other monster had gathered grass and shaped it into the form of a horse through some unknown means.
Though in Rei's mind, it was already practically settled as a lake monster. The fact that the horse's body was composed of aquatic plants made that all but certain.
(Multi Slash—a very practical skill. Though Death Scythe is already powerful with a single strike, so having multiple of those hit in succession means it'll likely be overkill unless the opponent is quite formidable.)
He scanned the area to make sure no other grass horses were lurking nearby, then returned Death Scythe and the Twilight Spear to his Misty Ring.
In the end, the Twilight Spear didn't get its turn this time, he mused.
"Hey, Rei. Do you know something about that monster?"
Seeing Rei stow his weapons, the adventurer apparently judged that the battle was truly over and approached to ask.
Rei silently shook his head.
Talking about that monster would naturally require talking about the lake—and since the lake was a secret, he couldn't say anything about it.
Sensing something from Rei's demeanor, the adventurer didn't press the matter further.
(For now, aside from the business with Anastasia's assistant, I also need to report that lake monsters are surfacing from places other than near the Birth Tower. ...Come to think of it, that's only natural.)
Until now, they had assumed monsters only emerged from the lake beside the Birth Tower. But from the monsters' perspective, there was no reason to limit themselves. Rather than deliberately heading toward a place where enemies lay in wait, it was far safer to come ashore where no one was watching—that much was certain.
That said, it would be a different story for ferocious creatures like the lizard monsters that had attacked Rei's group.
"Anyway... which part do you think would count as the Subjugation Proof Part?"
"No, that's..."
Partly to deflect the question, Rei's words left the adventurer hesitating.
The horse's body was genuinely made of grass. Nothing resembling a Subjugation Proof Part existed. If one had to designate something, it would be the grass scattered on the ground nearby.
"Do you think this grass would count as a Subjugation Proof Part? Or since it composed the monster's body, maybe as a material?"
"Ah... I wonder. I'd say that's a stretch, though."
In reality, setting aside the Subjugation Proof Part issue, Rei felt there was genuine potential for usefulness as a material.
But given the high likelihood that this monster had originated from the lake, he judged it would be unwise to let that information spread carelessly. If the grass turned out to be some rare medicinal herb, it would undoubtedly cause trouble down the line.
To prevent that, he needed to talk things over with the Guild first.
"It's an unknown monster, so I'll take this grass to the Guild for now and see what they say. If it turns out to be a material they'll buy—like a medicinal herb or something—I'll split the proceeds with you guys. ...That work for everyone?"
"I'm fine with that. You guys are good with that too, right?"
The adventurer nodded at Rei's words, then checked with his companions. Everyone agreed.
After all, they were the ones who had been struggling against an enemy that regenerated as soon as grass gathered and reassembled. Having been bailed out—and being offered a cut of the proceeds if the grass fetched a price at the Guild—there was no one inclined to refuse.
...If it had been some random adventurer off the street, it wouldn't have been strange for them to demand more of the money, or even all of it, if it served their bottom line.
But the adventurers currently working in the Treant Forest had been recommended by the Guild. The incidents at the lake and the Birth Tower, along with the appearance of High-Rank Monsters like the Cerberus, likely factored into that selection. These were adventurers with solid skills and, equally important, sound character. That careful screening was precisely why they wouldn't cause unnecessary trouble.
Though if they knew Rei's strength, it was only natural they wouldn't try anything with someone like him in the first place.
"Alright then, I'll go around gathering this up. ...Though collecting it all does look like quite a job."
The grass that had composed the horse's body had been scattered across a fairly wide area by Set's and Rei's attacks. Gathering it would be tedious work—Rei would have been well within his rights to find it bothersome.
Perhaps taking pity on his demeanor, the adventurers pitched in to help pick up the scattered grass, but...
"Huh? Wait, is this grass different?"
More than a few people found themselves confused.
The grass composing the horse's body was, technically, a water-weed-like plant, but plenty of them couldn't tell the difference at all. And with it being spring, the Treant Forest was currently lush and overflowing with greenery. The grass from the horse naturally blended in with the grass growing everywhere around them, making it difficult for some to spot.
In the end, those accustomed to that kind of work banded together to search... and within about twenty minutes, they had gathered most of it.