The Research Institute contacted me the next day.
They had identified the substance found within the magical beasts. The conclusion was simple: the drug was manufactured from materials harvested in the Former Demon Territory, and its primary function was to force biological mutations.
The results were largely as I had anticipated. The citizens of the Republic had likely ventured into the Former Demon Territory specifically to procure the raw materials for this drug. Their targets were the water and plant life saturated with high-concentration miasma. After years of dedicated research, it was entirely plausible that they could produce such a substance.
Ethically, of course, it was an atrocity. While illegal potions were common enough, an effect of this magnitude was unprecedented. This series of magical beast incidents had been triggered by placing individuals injected with the drug in various cities abroad. Since the transformation occurred after a significant delay, the abnormality remained undetectable until the mutation actually began. Their countermeasures against perception magic were thorough.
The manufacturer likely possessed a deep understanding of the arcane.
(To be able to manifest magical beasts anywhere without a hint of suspicion...)
I was hardly one to talk, considering I ruled over a kingdom of the dead, but the practice was undeniably inhumane. The world could not be allowed to remain a place where such things were easily executed. I would put a stop to it as soon as possible.
The Research Institute officially designated the substance as the "Magical Beast Drug" and planned to continue their analysis. They were currently attempting to synthesize a cure. Success was far from guaranteed, but it was an endeavor worth pursuing. While unlikely, there was always a risk that my own subordinates could be targeted. I could not afford to simply give up if that situation ever arose. Now that we knew the cause, I wanted to establish a defense while we had the chance.
(A cure is important, but I must pursue a more fundamental solution.)
If I continued to merely react to their moves, the damage would only mount. I wanted to seize the mastermind immediately, but their location remained a mystery. Even so, there was an action I could take.
The simplest solution was to destroy the Former Demon Territory, the source of the raw materials. These materials could not be easily cultivated; they were a unique byproduct of the specific magic power and miasma found in that region. Replicating that environment elsewhere would be a Herculean task—hardly a realistic option.
Therefore, as long as they continued to manufacture the drug, the Republic’s agents would have to return to the Former Demon Territory to harvest more. If I cut off their access to the source, they would be forced to rely on whatever stockpiles they already possessed. Their production speed would plummet, creating a significant flaw in their schedule.
I intended to find the mastermind during that window of opportunity. Once I identified who was pulling the strings, I could eliminate them personally. In terms of pure combat prowess, I was rarely outmatched. Unless I faced an out-of-spec entity like the Great Spirit, I didn't expect to struggle. If I could just find the enemy, I could bring this to a swift conclusion. Once the stockpiled drugs were seized and the victims captured, this incident would be over.
Just then, the doors to the Audience Chamber opened.
It was Grom. He didn't seem particularly agitated, nor did he look like he was there to deliver an urgent report.
"What is it?" I asked.
"No, I simply... I wondered if there was anything I might assist with, and so I have come to seek your presence, Maou-sama."
Grom spoke tentatively, as if testing the waters. The Demon King's Army was currently stationary, but he clearly wanted to contribute. I suspected he simply couldn't sit still and had come to me directly for orders.
"I see. I appreciate the gesture," I replied honestly.
Grom was as loyal a retainer as ever. I had no desire to discourage his initiative. I had been planning to head to the Former Demon Territory alone, but since he was here, I decided we might as well work together.
"It isn't a grand mission, but there is something I'd like you to help me with. Can I count on you?"
"Of course! For your sake, Maou-sama, this Grom would gladly leap into hellfire itself, indeed!"
Grom answered with gusto. Even if he did leap into hellfire, his skeletal frame would likely be fine; he’d probably just go for a stroll through the flames. Still, it was a sincere expression of his loyalty. It would be boorish to point out the logistics.
Grom and I teleported from the Royal Castle. We arrived in the dark, desolate wasteland of the Former Demon Territory. Grom looked around at the familiar gloom.
"This is..."
"The Former Demon Territory. We have to deal with this place first."
"Specifically, what do you intend to do, Sire?"
"I'm going to cleanse the atmosphere and then systematically destroy the region. I want to ensure it never produces raw materials again."
I had been considering this since I was at the castle, and it was the most logical priority. If I turned this land into a barren husk where not even a weed could grow, manufacturing the drug would become impossible—at least for the foreseeable future.
Grom stroked his jaw, sounding impressed. "Ho-ho... quite a bold strategy. Truly, you are the Maou-sama."
Despite his praise, his movements were slightly stiff. He seemed to be testing the air, trying to acclimate himself to the environment. This land was exceptionally harsh; a normal human would suffer physical trauma just by standing here. Even for a high-ranking undead like Grom, it required a moment of adjustment.
Once he seemed settled, I gave him his first order. "Try absorbing the miasma in this immediate area."
"Yes, at once!"
Grom nodded and extended his eight arms. He stood in a wide, firm stance and began to focus. The magic power and miasma suspended in the air began to swirl, funneled directly into his body.
Moments later, Grom dropped to one knee, groaning in pain. "Guh... this... this is quite... intense, indeed..."
Absorbing miasma that isn't one's own triggers a violent rejection. The sensation of a foreign energy invasive to the core is agonizing—like having one's body slowly torn apart. If one isn't careful, even the soul can be eroded. I had done the same thing back in the Valley of the Dead, so I knew his suffering all too well.
"The burden will ease once you grow accustomed to it. Hold on."
"M-Maou-sama...! Gwaaaaaaaaaah! This is nothing! Nothing at all, indeed!"
Grom roared and forced himself back to his feet. Immediately, the rate of absorption stabilized. The surrounding miasma thinned out and eventually vanished entirely, leaving a hollow pocket of clear air where the corruption had been. Grom had drained it all.
"Hmm. A success."
"Huff... huff... huff..."
Grom was panting heavily. He was clearly exhausted. Strictly speaking, a skeleton lacked the lungs to be out of breath, yet he was gasping all the same. The reason for this remained a mystery.
"Are you alright?"
"O-Of course... I... I can still go on, indeed..."
"Rest for a moment. After that, I want you to move to other sectors and absorb the miasma there. I’ll be moving through the territory to cleanse the rest."
"Understood..."
Grom sat down on the spot, evidently needing time to recover his strength. I left him there and teleported away.
I spent the following hours systematically stripping the Former Demon Territory of its magic power and miasma. I eliminated the few remaining demons I encountered and pulverized the landscape with a relentless barrage of Forbidden Magic. Grom joined the effort once he recovered, and our combined efforts accelerated the destruction significantly.
By the time we were finished, we had transformed the Former Demon Territory into a true, hollow wasteland.