Not long after, the soul flame in Momonga's eyes flickered.
With a trace of surprise, he withdrew his bony hand. The old man, who had already died, collapsed to the ground with a dull thud.
"Interesting. Corpus of the Abyss?"
Momonga stroked his chin as he pondered.
As the Alliance Leader of Zurrernorn, the old man's memories were similar to those of Nigun from the Sunlight Scripture. A certain type of mental restriction had also been planted in his mind.
However, compared to the Theocracy's techniques, which had been refined and passed down for centuries, the old man's seal was crude.
Momonga barely needed to exert any effort to dismantle it.
After browsing through the man's memories, he obtained quite a few interesting pieces of information.
[Corpus of the Abyss]
This was a secret organization of Undead magic casters established four hundred years ago.
It could also be regarded as the predecessor of Zurrernorn.
The old man, who served as the Alliance Leader, originally came from this organization.
At first, it was simply a gathering formed to ensure that their respective interests would not clash.
Undead were beings with infinite lifespans. When they pursued magical research, friction with others of similar standing was almost inevitable.
Devoid of the three fundamental desires that drive the living, Undead often developed other powerful cravings instead.
For Undead magic casters, that craving was usually an overwhelming thirst for knowledge.
Because of that, whenever conflicts over knowledge arose, the situation could spiral out of control.
Neither side would yield. What began as a dispute could escalate into a full battle for supremacy, and eventually turn into a war of annihilation that ended only when one side was completely destroyed.
When all the desires born from the living's three fundamental urges became concentrated into a single obsession, that desire could grow so intense it became impossible to suppress.
It was not uncommon for Undead to destroy one another in this manner. In some cases, opportunistic living beings would take advantage of the aftermath and wipe out both sides.
Thus, countless Undead ended up destroying each other simply because neither side would yield their monopoly over knowledge or magical items.
Under such circumstances, one Undead stepped forward.
He brought an end to those pointless conflicts.
Instead, he proposed that cooperation and trade within reasonable limits would be the wiser path.
And so, the [Corpus of the Abyss] was born.
In the beginning, it was founded by four [Night Lichs] and three [Elder Lichs].
There were only a handful of rules. Members who violated them would be attacked by the others. It was nothing more than a loosely connected association.
However, after roughly two hundred years, it gradually evolved into an organization with a well-defined set of rules.
At the same time, the number of Undead members continued to increase. The structure eventually consisted of seven founders in the Inner Circle and forty-eight members in the Outer Circle, along with additional members who joined later.
Altogether, it became a large organization with fifty-five members. The seven members of the Inner Circle had all grown into legendary Undead beings at around Level 50.
Within the organization, members generally had a rough idea of what others were researching.
This exchange of information existed to prevent duplicate research and the resulting competition over resources.
However, the truthfulness of the research each member reported could not be guaranteed. Most still maintained secret projects of their own.
The Undead within this organization could be broadly divided into two types.
The first type established their own forces among the living and used those forces to achieve their goals.
The second type had nothing to do with the living world, quietly pursuing their own objectives from the shadows of the world.
Very few members belonged to the first type. The overwhelming majority were the second.
As a result, the organization rarely caused any major disturbances in the world of the living.
After all, if one attempted to expand influence among the living as the first type did, it would inevitably attract more enemies.
Especially because Undead are considered enemies by all living beings. At times, the living would even set aside national boundaries and cooperate to eliminate them.
Because of that, the number of Undead who openly operated among the living grew even smaller.
Of course, there were also some who could quietly establish themselves in the darkness of the living world without being discovered.
But Undead capable of that level of subtlety were exceedingly rare.
(P.S.: For example, the one in Eight Fingers.)
As powerful individuals, each of them was the kind of being that could conquer a nation alone.
Every member of the organization possessed that level of pride, so there was very little cooperation between them when it came to their individual goals.
The Corpus of the Abyss had almost never acted like a true organization.
Each member buried themselves in magical research.
Decades would pass like that. Aside from exchanging information and discussing their findings with one another, they would hardly ever leave their strongholds.
That was why the organization existed only in rumor.
Almost no one in the world of the living even knew they existed.
Momonga found that style of management rather interesting.
It felt somewhat like the hobbyist mutual aid group from his former world.
And thanks to the restraints imposed by the Corpus of the Abyss, these Undead had remained contained.
Otherwise, they would undoubtedly have become an unprecedented catastrophe for this continent.
However, according to the old man's memories, the Corpus of the Abyss had faced an unprecedented crisis several centuries ago.
A powerful being discovered the organization and attempted to bring it under its control.
In the end, that provoked a fierce counterattack from every Undead in the organization at the time.
The details of the battle were unclear.
The old man seemed to have deliberately erased that part of his memory.
Judging from the instinctive fear embedded in his consciousness, Momonga guessed it had been a one-sided massacre.
In the end, the Corpus of the Abyss was utterly defeated and brought under the control of "that master."
From that point on, that master began using the Corpus of the Abyss's research to strengthen his own forces.
Zurrernorn was also born from the remnants of the Corpus of the Abyss.
However, compared with its former state, its strength had clearly declined drastically.
There was one point that especially caught Momonga's attention.
As for that master, the old man's memories held no clear impression at all, only a vague black silhouette.
It seemed the other party had deliberately concealed his true form.
But based on the combat strength shown in the memories of the Corpus of the Abyss, for someone to crush them so easily, Momonga estimated that person had to be at least above Level 70.
And that person had left behind two orders.
The first was to continue the research.
The second was to guard something that had been sealed.
The first was easy enough to understand.
After all, the Corpus of the Abyss's research really was valuable.
Improving specialized techniques to create even more advanced Control Undead spells.
How to use higher-tier magic.
Ways to strengthen Undead attributes.
Those were the fruits of the Corpus of the Abyss's centuries of research.
Some of those materials even made Momonga feel a surge of delight.
For example, giving Undead that originally lacked the ability to control other Undead that very power.
And the evolutionary advancement paths leading to higher-tier Undead.
Using the race and class framework of [YGGDRASIL], that should have been impossible.
But the Corpus of the Abyss had broken through that limitation.
(In the Elder Coffin side story, Keno's research was built on this foundation.)
(What should originally have been a realm only stronger beings could reach was achieved through the Corpus of the Abyss's research even with a weaker body, and it even surpassed the [Vampire Ancestor] class.)
(At the cost of greatly degraded abilities, it obtained the race [Lesser One - Lesser Divine Ancestor].)
"This trip has really been rewarding."
Momonga took out a magic crystal and stored away all the memories related to this section.
Setting Nazarick aside, as an Undead great magic caster, he was personally very interested in this material as well.
If the Corpus of the Abyss had not already been almost completely wiped out, Momonga would have wanted to invite every last member of the organization to Nazarick on the spot.
Then they could research magical knowledge for him day and night.
"Hmm..."
He removed the World-Class Item [Eternal Seal].
The familiar green light emerged, and calm returned to his heart once more.
Momonga looked around, and his gaze fell on the Abomination standing motionless nearby.
From the memories he had just reviewed, he now understood why this Abomination had given him such a strange feeling.
Tainted blood from the underground sealing altar?
Thinking that, Momonga turned to the side.
Khajiit was standing there respectfully.
Beside him was a large pile of items.
These were all things Khajiit had scavenged from the dead Zurrernorn members while Momonga was thinking.
There were fifteen leather bags in total.
Each one held several thousand common gold coins, for a total of around fifty thousand coins, weighing one hundred and fifty kilograms altogether.
There was also a bag of rare magical gemstones.
Scrolls that recorded spells.
A short staff imbued with magic, along with several other magical items.
With a sweep of detection magic, Momonga quickly grasped the details.
Looking at Khajiit in front of him, he could not help but nod.
Not bad. He really knew how to be diligent and economical.
That saved Momonga some effort.
Once they returned to Nazarick, he would give him some kind of reward.
Thinking that, Momonga raised a hand in a beckoning gesture.
The previously motionless Abomination immediately began to move, walking step by step toward the depths of the cave.
"Let's go."
After saying that, Momonga followed after it.
At the same time, he quietly took out a staff.
The blood-red gem set into it gave off a faint glow, driving away the darkness around him.
He was heading underground next.
In the old man's memories, that master had left behind two orders. One was research, and the other concerned the seal below ground.
For some reason, Momonga had a premonition.
This matter was important, extremely important.
It might even be connected to him in some way.
Seeing this, Khajiit immediately broke into a light run and followed.
As he passed the old man's corpse, he sighed inwardly.
"Farewell, teacher."
"Thank you for taking me in when I had fallen so low, and for giving me the ritual to transform into an Undead. Otherwise, I never would have met Naohara-sama and Momonga-sama."
"So please, help your student one last time."
He reached out and stored the corpse in his storage space.
Khajiit intended to transform it into a new Undead, one that would fight for him forever.
That was how he planned to repay that kindness.
Following the Abomination's footsteps, Momonga and the emotionally conflicted Khajiit continued onward.
Eventually, they arrived before a cave.
The pitch-black cavern seemed bottomless. Seeing the Abomination jump down without the slightest hesitation, the two of them followed without delay.
Darkness swallowed their vision once again.
The strange feeling in Momonga's heart also grew stronger and stronger.
"What could it possibly be?"