Looming over the corpses, the zombified demon controlled by Israfel expressionlessly reached down its hand. The process could be done remotely, but physical contact allowed for an easier and more energy-efficient process.
As it clasped the wounds of the dead, dense obsidian gas oozed out of the pores of its fingertips, dragging with it darkness energy already present in the surrounding atmosphere.
The energy, mixed with what demons referred to as the Attribute of the Dead, seeped into the exposed flesh. After fully permeating the interior, it then proceeded to envelop the outside as though forming a thin black Chrysalis.
The bloody and mangled bits torn open in the battle gradually began to mend. The gaseous energy solidified and structured itself in such a manner that it could act as 'living' tissue.
Coalescing at the sides of each tear, the energy slowly inched them together. The end result was patches of dark, coarse skin between the otherwise normal pale white the humans had, similar to the case with the zombified demons.
Once fully restored, the energy focused on navigating the nervous system and infiltrating the brain. Without the soul that would abandon its vessel upon death, control over the body was up for grabs. A simple network of darkness energy with the Attribute of the Dead would be able to effectively issue commands to it and receive feedback.
After completing the process, the new puppet stood up at Israfel's will and joined the others. When each of the humans killed joined his crew, he took a glance over at the still-breathing rogue that fell under his mental influence.
Just as was the case with zombies, darkness energy could gain preliminary control of the nervous system of living beings. However, competing with the soul over the authority of its own vessel was a monumental task for a Tier 4 Dark Mage.
Energy expenditure aside, just the complexity of the signaling and fine-tuning of the Attribute of the Dead placed a great mental burden on the caster.
Thinking of this, Israfel was internally face-palming himself as he looked with frustration at his blunder.
'Great Demon King, why didn't I just kill this fool first before making more zombies? Ugh, I must be the fool.'
Israfel wasn't actually a fool. On the contrary, he was exceedingly intelligent. The feat itself of controlling the human while simultaneously creating zombies at his level showed just how exemplary of a Dark Mage he was.
It was already pushing his limits using mind control while operating a zombie from his safe spot in the portal room. So much focus of his was placed on this incredible multitasking that he simply forgot how much easier it would be to stop and kill the fellow first.
Letting out a bit of a sigh, the zombie went and slit the man's throat, allowing Israfel to immediately release control.
Regaining his awareness, the man convulsed briefly on the floor. The realization of what his own hands had done to his friends brought more despair than the physical pain possibly could. His final moments were not of him internally begging for death, but rather pleading to Aureon for forgiveness.
The zombification process was quickly completed before Israfel altogether cut off connection with his undead and sat back against the wall.
"Fuck, what terrible timing. Couldn't they just have waited a few more days?"
He groaned out loud. There was certain information he was privy to that even these human adventurers were not.
A war between human nations was about to be declared a few days later. This intel came from high-level demon spies that covertly left their dungeons and observed important human figures. It was relayed through their portals to the Demon King himself before he then disseminated it to every other portal controlled by a demon.
Using this opportunity to take advantage of the chaos, the Demon King would cast a grand spell to empower the demons and the portals for the sake of his ultimate goal to cross into the world.
The consensus amongst the demons was that the humans would be pulling away from the dungeons to focus on the war. Therefore, the Demon King would cast the spell right at the declaration, to give the demons time to adjust to their new abilities as the humans made their preparations to set off.
Then, once they started to mobilize, the demons would leave their lower-level dungeon portals and head to whichever Tier 2 portal managed to advance to Tier 1. That would become the central base of the demons meant to bring forth their Lord.
"I should've just let them take my shit and be on their way. It wouldn't really have been a great loss…"
Although he lamented, he knew he wouldn't have actually done things differently if given another chance. The words left his mouth, but he didn't mean them.
Now, he faced the risk of humans coming back for revenge before they'd be too distracted with their war. But was he going to just give up his precious research materials?
Ever since he was a boy, he had overflowing admiration for his grandfather. He could vividly remember the childish giddy excitement his otherwise composed elder would show in the face of a new alchemical discovery.
He too would feel an equal amount of joy at his grandfather's happiness and would share in the celebration as he was lectured on the theory behind whatever experiment was performed.
The entire success of their family was owed to his accomplishments. Without the Noble Title of Viscount that he earned, they wouldn't be enjoying the monthly income, access to special resources, or quality education.
Now, his grandfather was gone, and the inheritance of the Noble Title was ending with his generation. Without earning the title himself, his family's future lineage would fall into decline.
'If only my father wasn't such a deadbeat.'
He scowled thinking of the loathsome man, so drastically different from the great figure he stemmed from. The title Israfel's grandfather earned would only be inherited for two generations without work put in by them to maintain it. His father just sat back and enjoyed all of the privileges, not in the least bit concerned about the future of his grandchildren that wouldn't be inheriting it.
So, whether it was to follow in his grandfather's footsteps and continue his fascinating research, or to earn the title himself with his own achievements for the sake of his family, he was doing everything he could.
Yet, those insufferable humans, so primitive in their ways that they'd probably just eat the flora for subpar effects rather than brewing potions, wanted to take away what was his? Because they thought they were entitled to it? Just thinking about it made Israfel want to kill them all over again.
"Ugh, Great Demon King, please just let them be too distracted by this upcoming war to come and take revenge… I'm just a low-level demon…"
***
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***
Everything in the world has its bane. Fire consumes matter. Water douses fire. As for darkness energy, it has its Attribute of the Dead stolen by light energy.
The humans didn't even understand this fact. They thought their made-up God simply gifted them the power to cleanse the 'Evil Energy' used by the demons. If asked, they wouldn't be able to answer what the Attribute of the Dead even was, considering that they didn't know it existed.
Demons knew, but they didn't know why. They couldn't see the structure of the attribute, but they could perceive how different versions of it affected the darkness energy containing it. Their perception of it was how they were able to cast spells communicating with the minds of bodies, using the signaling derived from different forms of the attribute to interpret stimuli and issue commands.
When exposed to light energy, the attribute would simply vanish. At the very least, they lost their ability to perceive it.
So, a convenient source of alarm demons used was to detect the energy changes when a Cleric approached. A shift in the atmosphere transferring new attributes to energy losing it would be distinctly noticeable.
A few days after killing the humans that came for collection, Israfel flinched at the response in the surrounding energy. Last time, he only discovered the presence of humans when seen by his zombies. Now, if he was detecting a Cleric before his undead found them, it likely meant they had even stronger control over light energy.
More powerful adventurers came for revenge.
'Just my luck. The war will be declared either today or tomorrow, yet they just had to come now.'
There was no use in complaining. Simply cursing them wouldn't make his enemies disappear.
'Well, hopefully, my preparations will do their part. I can probably handle a party of adventurers all in my Tier without tricks… but it's still good to be careful.'
He had set a variety of traps in anticipation of his eventual pursuers. It wouldn't do much good if they sent opponents stronger than him, but he didn't think they'd go that far. At most, it'd probably just be a party of Tier 4 adventurers.
He decided he'd just have his undead play out some hit-and-run tactics for a while to tire them out and ambush them. Ideally, this would successfully kill the Cleric capable of dealing with his mind control. Then, after they entered a weakened and exhausted state, he'd sneak in some mind control to finish them off.
Next to him was the previous party of adventures, walking around in their state of undeath. He contemplated using them to deal with the newcomers. It could possibly incite quite an emotional response. If done properly, he could make use of their hasty actions to more easily dispose of them.
'No, let's not take more risks than I already have.'
Psychological warfare was a double-edged blade. It could make individuals act in more than one way. They could let anger blind them and make foolish decisions, becoming easier prey. But, they could also let wrath become their fuel for battle. Fury at times would make fearsome opponents.
'You lot will be my bodyguards for now.'
Instead, he positioned some of his zombified demons that came with him through the portal not far from the caved-in entrance. They held some basic wooden bows provided to him before departing the Abyssal Realm along with quivers of arrows.
'Let's take out the Cleric first.'
Sensing the disappearance of the Attribute of the Dead, his zombies knocked their arrows and aimed at their nemesis. The moment the wall was breached, they let loose.
'Hmm, I guess it failed.'
Instead of cries of despair, his zombies were met with more illumination and a charging Warrior.
As a demon, neither he nor his undead needed light to see, so it was generally dark in the dungeon except for the portal room. It was pretty typical for the humans to use Mages with fire magic to see, so targeting them was also a good tactic to do after getting rid of the Clerics.
'Well, I guess this fellow is the type to let anger blind him. Maybe I should send out these zombified humans..'
He briefly pondered as he controlled the zombies to retreat, expertly having them avert the dug-out pit he made around the corner.
'What a fool. Too bad that won't hurt someone with his defense…'
The warrior ran right over the hole and fell inside. Following right behind him, a speedy human, probably a Rogue, just barely stopped herself from falling in as well.
'Too bad she didn't go in first. That probably would've killed her.'
While internally monologuing, he had his zombies fire off a few arrows as she was on the ground. Unfortunately, she side-rolled and got out of the way.
'Back to the next ambush site, I guess. Hmm, I haven't hurt any of them so far. Hopefully, the skeletons will be a bit helpful in tiring them out.'
After moving them to the next location and having them find cover, he was going to have the skeletons with their sturdy forms go serve as punching bags while the zombies shot from a distance.
However, the Great Demon King was smiling upon him that day.
Suddenly, the dungeon began to shake. He withdrew his consciousness from the zombie back to his body, only to see powerful ripples of energy surging out from the portal he sat next to.
It wasn't darkness energy, mana, or light energy. It was the same thing the portal was made of, the energy the Demon King learned to wield, soul energy.
It gushed out from the portal and wildly twisted the atmosphere, filling the room with chaos.
He barely remained standing as the energy, seemingly gaining interest in him, rapidly surrounded and entered his body.
It was incredible. The sensations that filled him were beyond amazing, to even get a taste of that overwhelming power left him in a state of ecstasy.
When it was all over, he felt his control over darkness energy had drastically increased. Deliberately expelling and absorbing it as per usual, he noticed how vast the amount was that he was in possession of.
'I'm Tier 3 now.'
He knew. He didn't have to fight with anyone. Be it the quantity of energy, or the types of spells now at his disposal, his power had undoubtedly advanced to the next Tier.
There was no need for concern anymore. With a great smile painted on his demonic visage, he sent a torrent of darkness energy to his skeletons and zombies.
He could now develop the zombies' flesh in more prominent ways, giving them sizeable muscles capable of exerting a great deal more strength than before.
The skeletons were also made of darkness energy, but instead of pseudo-flesh, it simply formed extremely sturdy crystals that connected to each other. Although they were called skeletons, they only resembled them in appearance. Their bones were darkness energy itself.
Now, they'd be even denser, even more compact, and resistant to damage. He had at his disposal Skeleton Knights and Zombie Knights as his minions. The fight could no longer be called as such; it was a slaughter.
When the humans went and encountered his newly advanced undead, it was a matter of moments before they were exterminated.
Israfel's mood couldn't be better. He was worried for days, and now everything was resolved.
There was one thing, though, that didn't seem quite right.
'Why is one of my skeletons lying on the ground?'