Out of habit, Zhang Xuan collected the manual of the Divine Eyes of the Ninth Netherworld into the Library of Heaven's Path before browsing through it. So, what he was reading wasn't the text in the sky but the compiled book in the Library of Heaven's Path.

The introduction still sounded fine, but when he began processing the formula to practicing the optic art, he swiftly realized that something was amiss with the technique.

"What's wrong?" Sage Kui asked.

The optic art was created by his teacher, and it was incomparably profound. There was no genius possessing the Eye of Insight who wouldn't be mesmerized by it. Yet, the young man actually frowned and said that there was a problem. What did he mean by this?

"This.." Zhang Xuan turned over to look at Sage Kui. "Elder, I would like to ask if there's anyone amidst the preceding sanctum heads who have suffered from blindness?"

"Blindness?" Not comprehending the reason behind Zhang Xuan's words, Sage Kui frowned. "I am only in charge of guiding and assessing the potential candidates for the position of sanctum head, so I don't really know much about their affairs."

He had died several dozen millenniums ago, and in order to allow his fragmented soul to survive as long as possible, he would only regain consciousness if a genius perceived to possess the Eye of Insight were to enter the examination grounds. Considering the limited time that he remained conscious, it was difficult for him to find out much about the affairs of the other sanctum heads.

"Then.. Pardon me for asking this insolent question, but was Ancient Sage Bo Shang's eyes fine?" Seeing that he was unaware of the matter, Zhang Xuan rephrased his question once more.

"My teacher has departed from the world shortly after founding the Sanctum of Sages.. and his eyes were indeed blind then." Sage Kui paused for a brief moment before adding, "However, with appropriate treatment, I think that his condition should be reversible.."

"Reversible?" Hearing those words, Zhang Xuan unwittingly shook his head as a bitter smile emerged on his lips. "I'm afraid that it'll be extremely difficult to do so, if not impossible altogether."

"Why?" Slightly surprised by Zhang Xuan's affirmative response, Sage Kui asked.

There were many books containing details about Ancient Sage Bo Shang's affairs in the Sanctum of Sages, but most of them were centered around the nobler and more positive aspects of him. Furthermore, it was only known in a very small, closed circle that he had lost his sight back then, so the news didn't spread too far. So, how did the young man learn of the matter?

Not to mention, to speak so affirmatively that it was nearly impossible to recover from his blindness..

"The reason lies in the Divine Eyes of the Ninth Netherworld!" Zhang Xuan sighed.

"The optic art serves to tap into one's potential through the Eye of Insight to unleash devastating might. In terms of prowess, it is indeed an incredible battle technique. However, the side effect is that each time the formation map was activated, it would inflict tremendous, irreparable damage to the eye. As time goes by, one would inevitably lose one's sense of sight!"

In fact, the very first flaw regarding the Divine Eyes of the Ninth Netherworld in the Library of Heaven's Path was the permanent loss of sight.

Regardless of whether one was an ordinary mortal or a cultivator, there was bound to be a limit to one's potential. The ability of the optic art in tapping into this potential in the form of formation maps was indeed formidable, capable of bringing forth great destruction in an instant. However, the damage that it would inflict on the caster was immense and irreversible too.

This was especially so since a human's potential couldn't be restored with any pills or means.

To make an analogy, this was just like how, in Zhang Xuan's previous life, a significant portion of talented athletes tended to have short lives. This was because they had sapped the potential of their bodies dry when they were younger. On top of that, the injuries they had sustained throughout the course of their career also remained as traumas, placing a great strain on their bodies. As a result, very few of them were able to enjoy the lifespan of an ordinary human.

What the Divine Eyes of the Ninth Netherworld drained was the optic nerves. It was possible to treat and change the eyes, but if one's optic nerves were to wither and die, there would be very little that one could do.

In other words, the optic art was fatally flawed.

To Saint realm cultivators, who possessed extraordinary senses and Spiritual Perception, it might seem like the loss of sight might not impede their fighting prowess significantly. However, the same couldn't be said about those who possessed the Eye of Insight.

In the first place, even without practicing optic arts, the Eye of Insight was already a very powerful gift in itself. The very ability to discern details more keenly than anyone else could play a deterministic role in the outcome of a battle. The loss of sight would mean the loss of this gift, which would result in a sharp decline in one's fighting prowess. On top of that, one might also suffer a huge setback in their state of mind as well, and that would prevent them from reaching greater heights in the future.

Hearing the young man's helpless sigh, Sage Kui frowned in displeasure, "I have practiced the Divine Eyes of the Ninth Netherworld for several hundred years now, but I haven't noticed any damage to my eyes. This is an optic art left behind my teacher, so I'll have to ask of you not to spread false rumors about it!"

It was not that Sage Kui was reluctant to believe Zhang Xuan's words, but he had also cultivated the optic art for many years, but his eyes were still completely fine. He didn't experience any discomfort or pain as a result from using the technique, and his eyesight hadn't been impaired either.

Given so, wasn't the other party's worries a little unfounded?

Besides, who was his teacher?

Ancient Sage Bo Shang, one of the Kong shi's direct disciples, honored as one of the Ten Apostles! The Divine Eyes of the Ninth Netherworld was a technique which Ancient Sage Bo Shang had devoted his entire life to developing, so how could there be such a fatal flaw to it?

This was a ridiculous notion in itself!

Even if there was a flaw in it, it shouldn't be something which a mere Primordial Spirit realm cultivator like the young man would be able to see through!

Knowing that Sage Kui would react in such a way, Zhang Xuan didn't lose his composure. Instead, he looked at the latter and said calmly, "Why don't I put it like that then? Elder, you mentioned that you have cultivated the Divine Eyes of the Ninth Netherworld for several hundred years now, but if I'm not mistaken, you weren't able to reach the third realm, right?"

".. Yes." Sage Kui nodded.

Due to his lack of talent, despite his hard work, he was still unable to catch up with his teacher's footsteps even up to his teacher's death. Putting aside the third realm, he wasn't even able to reach the peak of the second realm.

"If I'm not mistaken, when you first left this fragment of your soul here, you have just used the inferno to reforge your eyes and the frigid ice to temper them, allowing you to barely reach the second realm of the Divine Eyes of the Ninth Netherworld. At your current level, you are already able to see through the darkness with absolute keenness, as if it's a brightly lit room. However, in a real battle, you still aren't able to use the true prowess of the second realm, Asura's Wrath, right?" Raising his eyelids, Zhang Xuan said.

The first realm of the Divine Eyes of the Ninth Netherworld was Gaze of Deities and Demons, and the second realm was Asura's Wrath. Once one had mastered the second realm, with just a glance, one would be able to bring scorching inferno to the lands, as if hell had descended upon the world.

The first realm was mainly focused on mental offense whereas the second realm was a pure physical offense.

Those whose strength hadn't met a certain mark would stand no chance before Asura's Wrath at all, turning into cinders in an instant. Even those who possessed strength greater than the caster would find themselves placed in a very difficult position, unable to exert their strength freely as they wanted to.

Most importantly of all, the optic art could be cast at will. There would be no movements or anything else to warn one of the offense beforehand. Everything within the reach of the eye were possible targets, making it nigh impossible to guard against it.

It was for this reason that the Divine Eyes of the Ninth Netherworld was so famous, and the generations of sanctum heads were also deeply respected throughout the continent, possessing a standing higher than even that of the heads of the Zhang Clan and the Luo Clan.

However, as powerful as the technique was, it was extremely troublesome to cultivate it. Firstly, one had to reforge one's eyes with the inferno and use frigid ice to temper them. After which, one still had to go through many gruesome trials, and the slightest mistake in any of them could result in the cultivation of the Eye of Insight to fall through.

Even though Sage Kui hadn't executed any optic art so far, through Zhang Xuan's understanding of the Divine Eyes of the Ninth Netherworld, he was still able to roughly deduce the latter's proficiency.

"How.. did you know?" Sage Kui was astonished.

The other party's words were completely spot-on. When he first left behind a fragment of his soul in the Mountain Gate, he had barely managed to cultivate the Divine Eyes of the Ninth Netherworld up to the second realm, still a very far way off from reaching the third realm.

"Even though you are just a sliver of will at the moment, I can still see slight flames burning in your eyes. As weak as they appear, they seem to wield the potency to torch everything down to cinders. From that, it isn't too difficult to deduce that you have reached the second realm, Asura's Wrath." Zhang Xuan said as he leisurely strolled around the other party.

Since he had collected the manual of the Divine Eyes of the Ninth Netherworld into the Library of Heaven's Path, it took only a moment for him to assimilate all of the knowledge concerning it. With his current understanding of the optic art, it wasn't too difficult for him to deduce this much.

"Are you saying that.. you have already finished reading through the second realm of the Divine Eyes of the Ninth Netherworld?" Hearing those words, Sage Kui's body trembled in astonishment, and his eyes widened in shock.

It was just a moment ago that he had shown the manual of the Divine Eyes of the Ninth Netherworld to the young man, but in just a few breaths' time, the young man was actually able to accurately list out the various distinctive traits of the second realm.. Could it be that he had really managed to memorize all of it?

One must know that the manual of the Divine Eyes of the Ninth Netherworld consisted of over several hundred thousand words! Just browsing through it would take some time, let alone assimilating the knowledge. Back then, he had studied it day and night without rest after obtaining the manual, but it still took him two days before he managed to primarily grasp the optic art.

He even received his teacher's compliment for that..

And yet, the young man actually managed to memorize it all within just a few breaths? How could that be possible?

"It isn't too difficult to memorize the entire optic art. What's more important is interpreting and cultivating the technique." Zhang Xuan shook his head. He didn't reveal the slightest joy at having astounding the other party; on the contrary, he shook his head in pity as he continued on, "Correct me if I'm wrong, but while cultivating the second realm, Asura's Wrath, you should have seen red dots in your eyes from time to time. Also, there would be a slight itch in your eyes from time to time, and upon facing the wind, your eyes would tear up uncontrollably too. Worst of all, after casting Asura's Wrath, you would find yourself in a state of temporary blindness for roughly three breaths..

"May I know if there's any mistake in what I have said so far?"

"You.." Sage Kui couldn't believe what he was hearing.

He had indeed faced these conditions while he was cultivating the Divine Eyes of the Ninth Underworld, but back then, he thought that it was just a side effect from reforging his eyes with the inferno, so he didn't think too much into it. Could there really be something wrong with the optic art?

By the time he reached the second realm of the optic art, his teacher had already departed from the world, so there was no one whom he could consult these issues with. As a result, he could only fumble his way forward, hoping that he would be able to find the right path.

It was also true that he would suffer temporary blindness after casting Asura's Wrath, but he thought that it was a natural effect as a result of the excessive exertion of his strength in the casting of the optic art. Could it really be as the young man had said.. there was really a problem in the optic art?

"Asura's Wrath uses the eyes as a medium to channel a raging inferno upon one's enemies. Upon reaching Major Accomplishment, the flames would be able to cleanse all impurities and torch everything down into cinders. Without a doubt, it's a technique that wields astounding might, but it's highly exhausting on one's mind as well. Continued usage of the skill would cause the nerves that governed sight to age prematurely, thus significantly reducing the lifespan of one's sight. This is just like how the core of a formation plate would be depleted each time it's used. Once it reaches its limit, not even the most formidable of formation masters would be able to fix it."

Zhang Xuan shook his head in pity as he continued, "Even though you have barely reached the second realm by the time you left this sliver of will, the side effects have already started to show. For one, the immense strain on your eyes has resulted in the enlarging of blood vessels in your eyes, resulting in them appearing slightly red. Also, if I'm not mistaken, you should suffer from frequent insomnia too."

"You know that.. I have insomnia?" Sage Kui was flabbergasted.

For a cultivator as strong as Sage Kui, he could use cultivation to replace his need for sleep. Nevertheless, an occasional sleep now and then would still be a relaxing experience for both his body and mind.

In fact, most cultivators would still opt to rest from time to time.

Back then, when his teacher just departed from the world, he had to govern the entire Sanctum of Sages by himself, so he didn't have time to get much rest. Even when he tried, he wasn't able to fall asleep either. He had attributed the matter to his tense nerves, but could it really be related to the Divine Eyes of the Ninth Netherworld?

Now that he thought about it.. he seemed to recall that his teacher suffered from constant insomnia as well, and that had left him feeling lethargic frequently.

"Considering the damage the cultivation of the Divine Eyes of the Ninth Netherworld has caused to your nerves, it's inevitable that you would suffer from insomnia. Furthermore, as you deepen your mastery in it, your mind would start to wear down, resulting in frequent memory loss. More importantly.. your sensitivity toward colors would also start to dull, and eventually, the many colors of the natural world would appear to be nothing more than black and white to you.."

At this moment, Zhang Xuan paused for a moment before sighing deeply in sympathy. "In other words, total color blindness!"

"If I'm not mistaken, you should be suffering from such symptoms too!"