Peaceful times had passed.
To be precise, only my territory had been peaceful. On the continent, civil wars still broke out everywhere. Frank, Bretagne, Habsburg, Politunia… There was hardly anywhere safe from the ravages of war.
Hundreds upon thousands of refugees had fled. People's lives had become so destitute that they clung to nameless rumors—whispers of a utopia somewhere below the Black Mountains—and walked until they dropped. Fortunately, my domain was prosperous enough to take them in.
"This is land ruled by a Demon Lord. Is that still acceptable?"
"I heard the taxes are low. I heard there's no conscription either."
A village chief who had led his entire village here as refugees spoke in a haggard voice.
"They even protect us from Monsters."
"That is true."
"Oh, Goddess. Bless this man."
The village chief, before the very person who had brought war to the continent, prostrated himself and pressed his lips to the top of my foot.
"If that is truly the case, what does it matter that you are the Demon Lord? Great one—seven people starved to death just getting here! Please, take in me, my family, and all our villagers!"
I accepted them with generosity.
Farmland was distributed freely and equally. The tax rate was likewise set at thirty percent.
After one year, every last empty plot of farmland had been filled. I had offered undeveloped land at a mere ten percent tax rate, and even that was occupied within half a year. The population of my domain had long since surpassed the hundreds and swelled to two thousand.
The area near the Black Mountains was naturally fertile.
Countless spirits roamed the earth and the forests, so the soil never lost its vitality, and clouds rolling over the mountain range frequently unleashed torrents of rain. However, the abundance of spirits also meant that mana was plentiful—which in turn meant that Monsters were overflowing.
As long as Monsters appeared at random intervals, no human who valued their life would dare settle near the Black Mountains.
That was where I came in—I had completely blocked the Monsters' incursions.
Moreover, the tax rate was absurdly low. I didn't even levy a tax on grinding wheat at the windmill. I didn't tax the opening of markets either. As long as people obeyed the law, they had no problems whatsoever. To the common folk, this must have looked like a pure land of paradise.
All the farmland had been allocated. No more refugees could be taken in, even if they came.
However, by the time two years had passed, the dungeon had been completed down to the fifth basement level.
"I'm opening the Demon Lord's Castle to adventurers!"
At last, I set the <Adventure City Creation> plan into full motion.
The fact that humans kept pouring into the Black Mountains meant, conversely, that the Monsters were holding back their desire to attack purely on my orders. No matter how much I was the Demon Lord, the Monsters were bound to harbor resentment.
I housed all of those Monsters inside my dungeon. A dungeon where mana gushed forth without cease. The Monsters moved in without a single word of complaint.
At first it was only Goblins, but gradually Minotaurs, Lizardmen, Dwarves—intelligent beings you'd call Demonkin rather than Monsters—began trickling in.
I stationed the weaker species on the first floor of the dungeon and the stronger ones on the lower levels. Naturally, even among the weaker species, individuals that had grown in level were relocated underground.
And so, Dantalion's Demon Lord's Castle became a Monster department store.
You could call it a new-concept dungeon, I suppose.
In a typical dungeon, strong and weak creatures lived mixed together. Only powerful executives were permitted to stay near the Demon Lord's quarters—no Demon Lord had ever bothered placing weak Monsters at the entrance on purpose. It was only natural. Why would you let weak Monsters linger so that adventuring parties could grow accustomed to the Demon Lord's Castle?
When a dungeon was still unfamiliar, you threw powerful Monsters at the intruders and wiped the party out. That was the textbook approach.
But my goals were different from those of other Demon Lords.
"From now on, the Demon Lord and adventuring parties are no longer enemies."
Why would I wipe out adventuring parties? They were armed with expensive gear. Unable to trust anyone and living like vagrants, they carried their entire fortune on their person at all times. You could call them walking piles of gold.
"We're business partners."
Adventurers hunt Monsters in my dungeon and obtain mana-infused meat and bones. I collect the equipment and assets of those who die during the hunt. See? It's win-win either way.
The dungeon contained far too much mana, and if left unchecked the Monsters would multiply like wildfire. Adventurers taking care of them kept the population in check.
Better yet, Monsters that devoured adventurers often grew even more powerful. Those Monsters were recruited into my personal guard. Adventurers really are a grateful bunch.
"No more land to farm? Then put down the pickaxe and pick up a spear. Become adventurers and hunt the Monsters! The first floor is crawling with nothing but weak, pathetic Goblins. You can more than survive down there."
The more advanced unit types, like Goblin shamans, had already been moved to the lower levels. The first floor held nothing but the truly weakest Goblins and Slimes — the kind of monsters that farmers from this world could easily handle if they banded together.
Want to live? Then head for the dungeon!
The refugees who had fled to my territory picked up weapons one by one. Quite a few of them ended up dying from carelessness, but far more began earning a steady income. All it took was a little time before everyone and their brother was diving into the dungeon.
The great gears of the city's economy began to slowly turn.
First, word spread and mages arrived from across the continent and the Demon Realm.
"O Great Being, I consider this audience the honor of a lifetime."
"That sort of empty courtesy will suffice. I am well aware that mages are a race who break out in hives at the thought of etiquette."
The mage stroked his thick, overgrown white beard.
"My, my. As expected of the legendary Dantalion. Then allow me to get straight to the point. Our Lusatia Tower wishes to petition for the establishment of a branch within Your Excellency's territory."
"Heh heh."
I took a swig of wine.
"The goal is the materials that adventurers bring up from my Demon Lord's Castle, is it?"
"Oh, you saw through us at once! How could we dare hide anything from you? That is correct."
"For the purposes of magical research."
The mage beamed with a childlike smile.
"That's right! The meat and bones of Monsters imbued with mana are the finest materials for honing alchemy and magic. They cannot be compared to ordinary Monsters merely grazing on grass in the plains...!"
He looked at me with pleading eyes.
"O Great Being. I have heard that you graciously permitted humans to set foot in the Demon Lord's Castle. However, transporting Monster materials to other cities alone would cost a fortune. What say you? Our Tower would purchase the goods on the spot, immediately."
"I permit it."
I gave a nod.
It had been me who leaked the word to those mage towers in the first place. Having mages flood into my territory wouldn't be a bad thing at all. Well, Barbatos would feel differently—he went into spasms at the mere thought of humans settling in—but that was his problem.
"But, mortal. This is a domain where I alone, Dantalion, reign as sovereign. You mages shall never enjoy rights above those of commoners. Disabuse yourselves of any notion of being treated as nobility."
"This is what you mean?"
The mage bowed at the waist without hesitation.
"All that matters to us is the study of magic. The ranks and privileges spoken of in the mundane world are of no real consequence to us."
"I have only one question. I am a Demon Lord. You are of the human race. Yet you do not find it uncomfortable to plant your flag in a Demon Lord's territory?"
"O Great Being. That is precisely a concern of the mundane world."
The mage smiled.
"So be it. You are not the only one—there are many towers coming here."
"Th-there are? Hmph. I suppose that means we can't monopolize the materials after all... No, I suspected as much."
The old man's face fell. But the moment I added one more line, his expression brightened in an instant.
"Oh. Among them, there are towers making the crossing from the Demon Realm as well."
"The Demon Realm...? Is that—is that truly real!? You mean the Demon Realm!?"
Mage-towers of the Demonkin were even more powerful than those of human mages. The Demonkin simply had a greater knack for handling mana.
It went without saying that when it came to the advancement of magic, the Demon Realm stood a tier above the continent. Mages knew this, which was why they had exhausted every effort to summon Demonkin from the Demon Realm—begging them, please, teach us magic.
But the odds of summoning a Demonkin who actually knew magic were exceedingly slim. Even if one did manage it, getting the summoned Demonkin to look favorably upon humans was no easy feat. For mages, a Demonkin spellcaster was the stuff of dreams and an object of longing.
"Th-then we absolutely must establish ourselves here! Please, let us move in! We'll pay whatever taxes you demand, Your Majesty—just show us your mercy!"
The object of their longing wasn't coming as an individual but in the form of entire mage towers. Any human mage hearing of this would have their eyes pop out of their head.
I let a broad smile cross my face.
"A three-tenth tax rate on the buying and selling of Monster materials. On top of that, you will have the right of first refusal on the various potions and artifacts produced by the towers."
"Excellent! No, this is practically a giveaway! I'll sign the contract right now!"
The old mage forgot all about his dignity and huffed excitedly through his nostrils.
And so, a total of twelve mage towers were established in my territory. It was the birth of a human-demonkin joint magical research zone, something unprecedented in all of history.
Some towers specialized in alchemy, others in metal reinforcement. The towers carefully exchanged their own uniquely developed magical systems with one another, each stimulating the other's progress.
Several towers were so profoundly shaken by this that they relocated their entire headquarters over without hesitation.
"I've found that mixing potions into mana-enhancement spells and applying them to weapons yields extraordinary effects!"
"There might be a way to unleash powerful magic regardless of circle!"
"Don't hold back on the materials. This is exactly the kind of thing the money was saved for. Develop without restraint!"
The mages threw themselves into research with vigorous enthusiasm.
The weapons and potions produced during the course of their research were sold to me. I had the financial means to purchase every last one of them. Of course, my wealth wasn't infinite either, so the expenditures were considerable—but I couldn't have cared less.
I then resold these magical tools across the continent and the Demon Realm. The Kunkuska Trading Company stepped in as a middleman and took an enormous cut in brokerage fees, but an even more enormous profit landed in my hands regardless.
Monsters as raw materials.
Adventurers as producers.
Mages as processors.
A trading company to sell it all.
With all four pieces in place, I began raking in truly staggering profits. High-end magical tools were items whose demand would never dry up, so the future looked bright as well. For instance, potions that could extend one's lifespan even slightly were sold to the wealthy magnates of the Human Realm at exorbitant prices.
The profits emanating from my territory were so immense that Ivar Lodbrok, the chief of the Kunkuska Trading Company, came running to find me in a panic.
This was the same Ivar who had been turned away at my door and chased off in humiliation the last time. The fact that he could forget that humiliation spoke volumes about the sheer magnitude of the profits my territory was generating.
"Your Excellency. Please grant the Kunkuska Trading Company the exclusive brokerage rights for the mage towers' products."
"Of course, Ivar Lodbrok, the chief and I share a special bond, and I'd like to grant any reasonable request. After all, wasn't you, Chief Lodbrok, the very person who made the man I am today?"
When I gave a positive response, color returned to Ivar's face.
"But you still came wearing that fake doll's body. I'm sure I told you before—I said I wouldn't trust you unless you came in your real body."
"Y-Yes...?"
"Come visit in your own body as a Vampire. Otherwise, a deal is absolutely out of the question."
Ivar's expression soured.