Chapter 109: Unveiling the Secret of the Eyes of Death — Caliburn Unsheathed Again!
Shirou, along with the members of the Loki Familia, officially stepped into the passage leading to the artificial labyrinth and entered the man-made underground dungeon.
Since Loki had transferred all command authority to Shirou, even though he decided not to prioritize rescuing Riveria, Lefiya, and the others, they had no choice but to silently accept it, unable to protest.
Of course, the Loki Familia members were clearly dissatisfied — this was evident from the fact that they deliberately kept a certain distance from Shirou, clearly wanting to draw a line between themselves and him.
"This place really is identical to the real dungeon environment."
Once they were deep inside the artificial dungeon, Shirou was utterly amazed by its immense scale.
Just like the real dungeon, once they reached around the fifth floor, the overall size abruptly expanded significantly.
Even the ceiling height soared to several dozen meters.
Despite being underground, the space wasn't dark. The ceiling was embedded with radiant crystals emitting a soft glow, illuminating the entire floor.
Shirou could hardly imagine that such an enormous structure had been man-made.
Given the level of civilization in this world, even with divine blessings and powers, it was hard to believe such a vast construction could be artificially created. Shirou even doubted that one floor of this colossal maze could be built in just ten years.
It would take at least several decades of non-stop work to construct a single floor.
However, according to the Loki Familia, the artificial dungeon had at least over twenty floors.
If it took fifty years to build one floor, then twenty floors would require a thousand years to complete.
"A thousand years...? Why does that time frame sound oddly familiar?" Shirou muttered. "That craftsman named Daedalus — wasn't it said he built the Tower of Babel and Daedalus Street a thousand years ago?"
Because the time coincided too closely, Shirou couldn't help but suspect a connection between Daedalus and this artificial dungeon.
But Daedalus was a person from a thousand years ago.
Even if he had divine blessings, he was still human — there was no way he lived for a thousand years, nor could he have spent that long building such a massive dungeon.
So Shirou ultimately dismissed the idea that Daedalus was involved with this artificial labyrinth.
Due to the exceptional strength of the Loki Familia, their pace in conquering the artificial dungeon was very fast.
Even the mutant plants covering the floors were nothing more than prey before Orario's strongest expeditionary Familia.
Shirou didn't need to act at all. He simply watched as the Loki Familia members launched their offensives, easily clearing one floor after another.
But when they reached around the tenth underground floor, the werewolf Bete suddenly stopped in his tracks.
"Further ahead is where we encountered the followers of Death God Thanatos," Bete said grimly, his expression turning severe.
He was clearly recalling their previous confrontation with Thanatos Familia when Finn had led the team.
Not only had they suffered a crushing defeat, but Finn himself was seriously injured, forcing them to flee for their lives back to the surface.
For someone as competitive as Bete, such a humiliating loss was incredibly hard to accept.
"The followers of Death God Thanatos..."
Shirou looked around thoughtfully.
He recalled Loki's description: on the eleventh floor, Finn and the others had encountered Thanatos Familia's Level 6 member, Valletta, surrounded by bizarre monsters.
Those monsters, shaped like eyeballs, could split infinitely and attack over limitless distances without needing to be observed by the naked eye.
Just from the description, Shirou understood how troublesome those eyeball monsters were — no wonder even a top-class Level 6 like Finn couldn't deal with them.
"What should we do?"
Facing the likely presence of the Thanatos Familia ahead, the Loki Familia members all turned to Shirou with tense expressions.
Though they disliked Shirou, he was the only commander now.
As an elite expedition Familia, they knew that obeying the commander before battle was essential. Otherwise, they'd suffer needless casualties from chaotic combat.
"This is the enemy's stronghold. They're bound to be heavily prepared. So rather than making preemptive plans, it's better to improvise on the spot," Shirou said, waving his hand. "Besides, to be honest, I don't think we've built enough trust. On the battlefield, half-hearted trust only leads to disaster."
Though his words were unpleasant, they were undeniably correct.
Just seeing Shirou made them instinctively hostile, let alone following his commands in combat — it could easily have the opposite effect.
In the end, with no plan at all, the group pressed forward.
Soon, strange floating eyeballs began appearing in the air ahead, just as Loki had described.
And at the center of those floating eyeballs, the figure of a woman slowly appeared before them.
Her body was covered in scars, her short hair nearly white, and her twisted face looked nothing like a woman's. She stared at them with a warped expression before speaking in surprise:
"Oh? You've come back so soon, Loki Familia? I thought you'd be too afraid to return underground."
"Valletta of the Thanatos Familia, I presume?" Shirou glanced at her and immediately understood that this ominous woman was the Level 6 follower of the Death God.
"Oh? Who might you be?" Valletta asked curiously. "Where's my beloved Finn? What happened to him?"
"My name is Shirou Emiya," he replied calmly, then asked with curiosity, "You seem to hold a deep grudge against Finn. What's the story there?"
"Heh, that damned Finn personally destroyed my Familia!" Valletta said with a cruel smile. "A few years ago, our dark faction ambushed the Loki Familia with the goal of taking Finn's head.
But that damned little pallum used his intuition to sense our trap and struck back, attacking our home base!
After our god returned to the heavens, my abilities were sealed, and I nearly died.
If not for Lord Thanatos's blessing, I wouldn't have survived.
That's why I hate Finn — I want him to suffer worse than death. I won't let him die easily.
He'll taste torment like never before!"
"I see..."
After learning about Valletta's grudge against Finn, Shirou simply nodded.
He wasn't truly interested in the backstory — this conversation was just a distraction so he could observe the surrounding eyeballs.
According to Loki, these eyeballs had a very unique trait: if observed, they would take a visible form; but once unobserved, they could attack from anywhere over an unlimited range, and even their forms would vanish completely.
Shirou couldn't visualize what that would look like just from a description, so he decided to experience the situation himself and uncover the secret behind these eyes.
"Alright, I'm not really interested in your pointless history with Finn," Shirou said, waving his hand. "And I'm sorry to say — just like your previous Familia, the Thanatos Familia you now serve will also be utterly destroyed by me!"
"What did you say?!" Valletta widened her eyes. "I've heard the rumors about you, Shirou Emiya. Supposedly, you've defeated multiple gods.
Even our dark factions can't ignore you anymore.
But that ends today.
The Thanatos Familia is nothing like those other trash Familias.
We will bring true madness and destruction to this city!"
As her words fell, Valletta directly commanded the eyeball monsters to attack.
In an instant, countless eyeballs gathered from all directions.
"Die beneath the power of the Eyes of Death!" she shouted.
Valletta referred to the surrounding eyeball monsters as the "Eyes of Death."
Shirou took note of the name as he watched the Loki Familia members engage in battle with the creatures.
When these eyes were being observed, they behaved like ordinary monsters — slow, with mediocre combat ability.
Even Level 3 members of the Loki Familia could destroy them in droves.
However, the real issue emerged after the eyeballs were destroyed.
The defeated eyes didn't truly die — instead, they split, increasing in number. As the quantity rose, the team could no longer visually track all of them. Some unobserved eyeballs then lost form entirely and began long-range assaults in a waveform-like manner on everyone present.
"This sensation is..."
Bruises and wounds appeared on Shirou's body out of nowhere.
Even though no monsters were nearby and no clear attack had occurred, it was as if he were being assaulted from every direction.
And Shirou wasn't alone — almost all the Loki Familia members present were struck by these invisible attacks and began to move sluggishly.
"This bizarre situation again, damn it!"
The werewolf Bete cursed in frustration.
Clearly, this was his second time experiencing this incomprehensible phenomenon, and for someone like him who preferred direct combat, the invisible assaults were intolerable.
Even Ais, though facing it for the first time, struggled just as much. Despite being Level 6, she couldn't fully evade the attacks from the eyeball creatures, and her injuries continued to mount.
"Heh heh, heheheheh!" Valletta laughed wildly as she witnessed everything. "Fools, how foolish! You're still just as foolish, Loki Familia!
If you can't even grasp the true nature of the Eye of Death, then you're simply incapable of being my enemy!
All I need to do is wait until you've been worn down and are too weak to resist, and then I'll easily take care of you!"
Valletta's words seemed to reenact the scene of Finn and the others being defeated.
Back then, Finn was probably exhausted from dealing with the endless, even increasingly numerous eyeball monsters, and in the end was ambushed by Valletta when his guard was down—leading to him being gravely injured.
The current Loki Familia was in the same situation.
Even Ais, a Level 6, was unable to handle the increasing number of eyeball monsters. Once her stamina was completely drained, she would inevitably be ambushed and seriously injured by Valletta, who was of the same level!
For a moment, the members of Loki Familia all wore grim expressions.
Everyone's faces became clouded with despair.
They were already demoralized due to the absence of Finn and Riveria, and now they had encountered an enemy that even Finn had once been unable to handle. Naturally, their outlook became pessimistic.
Although Ais still had some strength left, she was merely a strong combatant and could not compare to Finn or Riveria when it came to analyzing the battlefield and giving commands. She was unable to reverse the situation.
Just as the oppressive atmosphere within Loki Familia worsened, and some members even began to lose their will to fight, Shirou's gaze remained firmly locked on the eyeball creatures before him.
"Something that keeps splitting apart after being destroyed... it's tangible when observed by the naked eye, but once it loses its observer, it becomes illusory... this feels like something I've heard of before…"
In that instant, Shirou's brain began working at full speed.
He tried to extract all the knowledge he had acquired in both this life and his past life, attempting to find a concept that could explain the existence of these eyeball creatures.
However, no knowledge came to mind that fit the concept, and he couldn't imagine what species these eyeballs even were.
Just as Shirou furrowed his brows and was about to abandon his investigation and temporarily retreat, a flash of memory suddenly appeared in his mind.
It was something that had happened before he crossed over into this world.
Before the battle with the Ainsworth family took place, Emiya Shirou had merely been an ordinary high school student.
The only extraordinary thing in his life was his younger sister, Miyu.
As a special existence known as a "Child of God", Miyu was essentially a living wish-granting device. Her soul was itself a physical manifestation of the Holy Grail.
Shirou's adoptive father, Kiritsugu Emiya, had discovered this living "Holy Grail" and racked his brain trying to figure out how to use her power to save the world—but ultimately found no way and died of illness.
Though Shirou was Kiritsugu's adopted son, he did not inherit his adoptive father's ideals. Not only did he have no intention of using Miyu, he actually wished for her to live a normal life.
Since Miyu was unable to attend school, Shirou even took it upon himself to educate her personally, starting from elementary through high school-level education.
To his shock, Miyu's ability to absorb knowledge was beyond imagination. In just a few months, she had mastered all elementary through high school subjects, even surpassing Shirou's own understanding.
Eventually, Shirou had no choice but to purchase university-level textbooks for Miyu to self-study.
Unsurprisingly, Miyu quickly mastered all the content in those books as well, forcing Shirou to seek out cutting-edge scientific theories for her to absorb.
It was during that period that Miyu became particularly fascinated by one concept: quantum mechanics.
Miyu believed that quantum mechanics might provide a scientific explanation for the existence of the soul.
The reason a "Child of God" is born as a Holy Grail is because of the uniqueness of their soul, and Miyu wanted to understand the essence of the soul from a scientific perspective.
Shirou didn't quite understand what Miyu was doing, but he chose to support her anyway.
He collected as many books on quantum mechanics as possible and gave them to Miyu.
Miyu immersed herself in the sea of knowledge and eventually became an expert in the field.
Because she wanted to spend time with her brother, she often brought up various topics with Shirou, including many discussions on quantum mechanics.
Using terms even an ordinary person could understand, Miyu explained to Shirou that the essence of quantum was "wave-particle duality."
More specifically, in the microscopic world, all matter exists in a superposition of two states: physical and non-physical.
When observed, microscopic particles collapse into physical reality. But without an observer, they only exist as a possibility.
There are two major experimental models that illustrate this theory:
Schrödinger's Cat and the Double-slit Experiment.
The former is well-known to many people.
It involves a poor cat locked in a box with poison gas that may be released at random. As long as the box remains closed, the cat is both alive and dead in a state of superposition.
Only by opening the box and observing it can the cat's state collapse into a definitive reality—either alive or dead.
The Double-slit Experiment is more scientific and clearly demonstrates the nature of reality.
In this experiment, a beam of light is emitted inside a sealed box, with a barrier in the middle that has two narrow slits.
One might expect that the light, passing through the two slits, would create two bright lines on the opposite wall.
But in reality, the experiment produces dozens of light bands of varying shapes on the far side of the box.
This strange result occurs because people often assume light is made of particles—a beam splitting and passing through the two slits.
But in truth, light behaves like a wave.
As the light passes through the slits, it produces ripple-like wave interference, much like overlapping waves on water. These waves create the multiple light bands seen in the experiment.
Of course, that's not the key point of the experiment.
The real focus is this: when the experiment is run normally, dozens of irregular light bands appear, proving that light behaves as a wave.
But when a detector is added to observe the light at the slits, the result collapses—only two light bands appear.
In other words, when there is an observer, the light reverts to behaving like a particle.
This is known as the Observer Effect in the quantum world.
The same object appears as physical matter when observed, and becomes a wave—ephemeral and intangible—when not observed.
Shirou, not being the brightest, could only grasp the theory to this extent.
Miyu, far more intelligent, noticed the link between quantum mechanics and the soul.
She tried to scientifically explain the essence of the soul.
But she never had enough time to finish her research—Ainsworth's threat destroyed their peaceful life.
In the end, Miyu only managed to intuitively grasp that a soul, like a quantum particle, might simultaneously possess dual characteristics—and possibly even be affected by observation.
In other words, if someone could observe the soul clearly enough, they might be able to collapse it from a vague, ethereal form into a tangible substance.
Now, seeing the Eye of Death summoned by the Thanatos Familia, Shirou felt it resembled the light bands from the double-slit experiment.
Both shared the traits of continual division and collapsing into physical matter when observed.
According to Miyu's research, the soul is also a kind of quantum entity.
Therefore, if her theory was correct, then the true nature of these Eyes of Death was likely this: a soul of some kind!
Just like a beam of light transformed into countless interference patterns through a medium, the infinitely multiplying eyeballs could also be the projection of a soul being diffracted through a special mechanism—interfering with itself, endlessly replicating.
If this was all true, then somewhere on this stage, carefully prepared by the Thanatos Familia, there had to be a key component: the equivalent of the double slit!
It might not be a literal slit, but it must be the source of this infinite soul projection!
"If such a thing truly exists, then it can only be in one place!"
Shirou scanned the area and quickly noticed the only unusual spot on the tenth underground floor—directly behind Valletta.
Behind her stood a large, unusually shaped door. Two intricate magical circles were carved into the door, continuously operating.
The moment Shirou saw this, he made a decision.
He shouted to the Sword Princess beside him, "Ais, cover me!"
"What?!"
Ais looked confused, not yet understanding Shirou's intentions. But then she saw him suddenly draw a stick-like object wrapped tightly in cloth from behind his back.
When Shirou tore away the cloth, a long sword of solid gold appeared before everyone's eyes.
At the sight of the sword, Ais inexplicably felt a sharp sting—as if her very soul was being shaken by the sword's aura!
"Members of the Loki Familia, get out of the way!"
With that said, Shirou didn't bother repeating himself.
He raised the sacred sword high above his head, and, aiming at Valletta and the door behind her—he swung it down with all his might!
"Caliburn!"