“Shortest possible explanation of how Dungeons work: absorb stuff and gain the ability to recreate it.

“With that stuff, you make structures and reinforce them with mana to the point where they’re functionally indestructible at your rank, make as much as you want as long as you don’t block access to your core. The same goes for traps, they can’t directly block access. For example, poison mist needs to either disperse eventually or be passable by someone of your Rank without crippling or killing them.

“As long as you have mana and your core is still accessible, go nuts.”

Not being able to physically or metaphysically block his core didn’t make a whole lot of sense to Thomas, especially how it worked with traps, but he was also fully aware of the fact that now wasn’t the time to ask. Especially as he’d just torn a strip off Elias for not explaining the important shit up front.

As much as Thomas wanted to interrogate the fairy about every aspect … Dungeon-ing? he had a job to do. Make sure that their next battle wasn’t won by the grace of God, but by a powerful and well-thought-out defense that could win repeatedly and reliably.

So he kept his trap shut and filed that topic away for later. Because there would be an interrogation, about this and any other topic that came up before then, come hell or high water.

“Monsters are simple, you can create as many as you can make by spending your entire mana pool in one go, and that’s the maximum you can have puttering around at any one time. But monsters below your current Rank are halved in influence cost for every Rank below your own. They’ll still cost the same after ranking up, but you can have a ton of them.

“You can also enhance monsters, raising them up to your current Rank after they’ve fought a little, and I’ll tell you how to create boss monsters once you’re able to do so.

“And you can only start to create sapient creatures once you’re at C-Rank, irrespective of the creature’s Rank.”

So, Thomas had everything around him to build his Dungeon with, from the materials to the exhibits. Though he was also pretty sure there were some awesome things just outside the room, through the door and down a short corridor into the gallery of mammals, which not only held several bears but also a friggin sabertooth tiger.

But before he got fancy, he needed to put up some rudimentary defenses.

Unfortunately, without that “System” of Elias’, Thomas was going entirely by feel, his magic washing out into his “territory”, which currently only consisted of a single room, and beginning to absorb creatures, removing various bloodstains when he struck them. The blood didn’t grant him any new patterns, but he was able to differentiate between the different people who’d bled all over the place.

There was blood here from a lot of different sources. Dozens of people had been not just hurt but injured badly enough for their crimson lifeblood to splatter about the place. They were most likely dead, eaten by creatures like that lizard.

And as for the patterns, mostly, he went for the big stuff, an elephant, a rhino, a boar, and a prehistoric creature called an arsinoitherium.

The last creature had actually been present as a fossil, but he’d taken a chance and it on the off chance that he’d be able to use it.

It basically looked like a rhino, but one that had two horns shaped like traffic cones, side by side, giving the creature a massive “V” on its nose. However, upon absorbing it, an extra bit of information appeared in his mind, informing him of the fact that the creature was actually closely related to his hippo.

Mostly, it looked like it’d be lighter on its feet than the rhino, being taller and less squat, though it lacked the armor of the modern beast.

And considering that he’d been able to get a monster from a fossil once, there was a good chance he’d be able to grab some dinosaurs once he reached that particular exhibit.

However, he also grabbed a tiny, adorable deer thing called a blue duiker. It was the smallest creature he’d seen on his first pass through the room, and in the absence of a System to tell him how much mana he had, he needed a yardstick, something to compare his expenditure to.

Making the actual comparison was something he’d planned to save until later, but somehow, it was interpreted properly automatically. The hippo cost about as much as nine duikers, the rhino would cost as much as a dozen, an arsinoitherium was worth fifteen, and an elephant twenty.

But that only worked when he was able to directly compare creatures in the part of his core that held his patterns. His pool of available magic was unavailable for direct comparison.

The only thing he could tell was that his mana pool was big enough that summoning a single duiker barely caused it to dip.

On the other hand, when he’d summoned the elephant he wanted to use as a final boss, a large chunk of his available energy vanished, almost a third. However, at the same time, Thomas could also tell that his energy pool was nowhere near full, and he’d already summoned a ton of creatures before he’d thought to try that out.

Right now, he had a few defenders sitting around, including a five-ton African elephant ready to sit on anything that disturbed him, which stood right in front of his core

The rhino and arsinoitherium, meanwhile, were on opposite ends of the room, staring at the entrance, ready to charge. He’d gone ahead and removed all ground-level obstacles while they got into position, not just the animals he’d absorbed to turn into monsters. Organizing his core afterwards had been a pain, but he’d managed it.

Two hippos, a rhino, a “sort of” rhino in the arsinoitherium, and an elephant. And the duiker, he supposed, as he hadn’t gotten rid of it after summoning one to see how much of his mana it ate.

That should be enough to deal with another lizard if it decided to show its ugly face.

Onto the making of the walls.

Right now, his main priority was reshaping the room to increase the length of the path between the door and him.

Right now, the door was maybe fifteen meters away from his core, all one would have to do was walk inside and turn left and that’d be it.

Love this novel? Read it on Royal Road to ensure the author gets credit.

So he put up a wall around the door, leaving only one path forward, the stairs to the mezzanine that ran the entire circumference of the room. Then, he extended the mezzanine’s railing upwards to entirely cut it off from the room, forcing those who entered to walk all the way around the second set of stairs, on the opposite side. Cramped confines, with barely any light, perfect for any small creatures that he eventually picked up. Badgers or something, if he could find one.

For now, though, he just summoned an arsinoitherium up there. It’d charge when it saw something, and there was no dodging up there. One would either have to kill it before it got up to speed or run.

As for the main room, he cut it in half with a wall that connected both stairwells. The first would hold the rhino and the first arsinoitherium he’d summoned, the other the elephant and his core. He also took the time to slap a layer of concrete over the armor that had supposedly belonged to Elias, lest someone steal it. It wasn’t like they could use it just yet, and based on the energy it emitted, absorbing it would be fatal.

And the blue duiker stayed with the core as well. It was cute, and that was all the justification he needed.

At first, he’d considered putting it in the corridor, and have it do puppy dog eyes at potential invaders as they killed it for some psychological warfare, but decided against it. People who fell for something like that would probably not be invading dungeons, and animals would just be glad for the meal.

“Is now a good time to explain some more stuff? Namely, how you grow and why I’m not as helpful as I could be,’” Elias asked.

“You’re not being helpful? … You don’t say …” Thomas replied sarcastically.

“Yeah, yeah, why don’t you get it all out of your system,” Elias sighed.

“Nope, that was it. Go ahead,” Thomas grumbled.

“Alright,” Elias flitted closer to Thomas’ core and began to explain. “Dungeons are powerful entities that warp reality around them, the living incarnation of the concept of ‘challenge’.

“They’re capable of creating structures and manifesting powerful defenders from the beasts that fall within and grow in power when invaders die inside.

“However, any invaders that succeed in delving into one’s depths will come out the stronger for it, however, their powers may function. Cultivation bases are strengthened, mana channels are empowered, XP is granted, monsters absorb whatever evolutionary energy they require, and so on.

“It is a Dungeon’s purpose to be enticing to potential delvers to grow while becoming neither a deathtrap nor pushover.

“As a part of their nature as incarnations of challenge, Dungeons cannot create no-win scenarios for those at their own rank. Some beings may simply be too big to enter, have a severe aversion to materials used in their construction, but the dominant local sapient species must be able to reach the core in theory.

“That means no impassable tunnels on the way to the core, whether they’re blocked by traps guaranteed to lead to death or a simple wall. In addition, they cannot alter their layout to directly affect invaders, for example, by dropping rocks on them, nor can they easily do anything in the vicinity of living beings that are not a part of the Dungeon.”

“Build defenses, wait for invaders to show up, send them packing, grow in power. And don’t create a deathtrap or no-win scenario in the process. Sounds simple enough,” Thomas summarized.

“It really isn’t,” Elias grumbled. “The issue is that most Dungeons tend to go a bit … overboard in the lower Ranks and drown their worlds in blood as they grow. I’m not saying you have to be a utopian resort full of rainbows and puppies, but I’d like you to not become one of the really bad ones.

“In addition, Dungeons’ world-warping abilities can cause serious issues if they try to affect certain things without the control gained at the higher Ranks. I’m not telling you what they are, I’m not even going to mention the concepts, until you can use them safely.”

“What if I came up with the ideas on my own?” Thomas asked. It made sense that the “simple” Dungeon Elias believed him to be would not be that smart, but he could imagine what ideas could end in tragedy if he messed with them. Antimatter, unnaturally dense materials, etc.

Control over his manifestations was sadly something he lacked. He could directly recreate materials he absorbed in the exact shape he’d absorbed, and create large, simple, shapes like squares or circles, but something more complicated, writing for example, was functionally impossible at the moment.

He’d figured out he could absorb or create several small chunks of material to eventually create larger constructions, but that took an insane amount of both mana and time.

As things stood, he wielded his power roughly, often tearing out large chunks around the thing he wanted to absorb, and then later filling in the gaps. For some reason, just slapping more material into existing holes wasn’t particularly complicated.

“I’ll know if you come up with something like that,” Elias replied. “If.”

Oh, screw you, Tinkerbell. Thomas sighed internally. Don’t kill the fairy, Thomas, don’t kill the fucking fairy …

He somewhat understood the issue, the source of his advisor’s caution, but that didn’t make it any less grating.

On to digging some pit traps with spikes at the bottom for some distraction!

They weren’t particularly complicated, he just absorbed the ground underneath the carpet, spent some more time cautiously wearing down the bottom of the carpet to make it thinner and weaker, ready to tear the instant someone stepped on it.

And finally, he placed a series of sharp railing chunks at the bottom. One of the bits he’d accidentally “eaten” had turned out to have one relatively blunt and one incredibly sharp end. The blunt ends went into the ground and the sharp ones pointed skywards.

“You know, I was thinking,” Thomas said off-handedly while putting in some of the finishing touches. “Of all the worlds you’ve ever been to or heard of, you’ve never heard of a hippo, right? But you know about Dire Lizard- … is the species name Lizardmen or Lizardpeople? Whatever. You know about them, right?”

“It’s Lizard people, but I’m not sure I know what you’re getting at,” Elias stated from his perch atop the duiker. He’d decided that the top of the adorable creature’s head was now his seat and settled down there. Thomas’ only response had been telling the duiker to leave the fairy be, and not throw him off.

“My point is that you’re right, a hippopotamus looks like a tub of lard at first glance, and they apparently don’t naturally occur on the same worlds as Lizard people. But that thing was scared of my hippo.

“So, either that thing was smart as hell and recognized the hippo as a threat before the fight … or it actually knew what a hippo was.”

“And I’m guessing you have an idea about what that reason is?” Elias responded. He was currently sprawled atop the adorable deer’s head, and looking quite bored.

“Yeah. If you got turned into a Dungeon Fairy, and I got turned into a Dungeon Core, what’s to say that someone else didn’t get turned into a Dire Lizardperson? What if there is a whole bunch of people out there who got transformed?”

“You’re not human, you’re a rock trying to pull a sca- … HEY!” Elias yelped as his “seat” suddenly bucked him off. Shooting Thomas’ core a filthy look, he added, “The rest makes a weird sort of sense. People with the powers of monsters … that is never good.

“Human cunning and monstrous strength is a potent combination and generally, those kinds of drastic permanent transformations tend to wear on their victims’ minds even if no new urges or compulsions accompany the shift. This is going to get ugly. Almost as ugly as they’re going to get if you don’t knock off that scam of yours!”

Oh, for fuck’s sake … if Elias kept his up, shit would really hit the fan, one of these days.

Thomas considered trying to have one of the creatures drool on the Fairy but figured that might be easy to misunderstand as a death threat. While his stubbornness was irritating to the extreme, Elias was useful. And who knew, maybe Thomas might be able to win that argument one of these days.

Thankfully, before he could escalate things, the target of his ire decided to flit out of the room.

“I’m going to scout, see you in a bit.”

“Leaving to cool off, would if I could … jackass,” Thomas muttered once the fairy was out of sight.

But without the little, bronze-winged, chatterbox around, he began to fall deep into thought. What the actual fuck had happened?

He’d turned into a rock, and that rock had magical powers, while everyone else who’d been in the museum at the time had been slaughtered.

Had the museum changed places, or had a massive jungle suddenly been dumped onto central London?