Taking out the black book, Chu Ning used his Divine Sense to directly start reading the content of the Third Layer of the Refining Spirit Technique.

He then continued to read further down.

Sure enough, the content of the Fourth Layer of the Refining Spirit Technique, which was inaccessible before, could now be viewed.

"The cultivation of this Fourth Layer of the Refining Spirit Technique is much more profound than the first three layers.

If I’m not mistaken, this is probably originally intended for Golden Core Cultivators."

Chu Ning spent a long time before he finished reading through the entire Fourth Layer of the Refining Spirit Technique.

He silently sighed to himself.

If not for the series of treasures he obtained that greatly enhanced his Divine Sense, it would have been difficult to cultivate the Refining Spirit Technique to the Perfection of the Third Layer.

Immediately, Chu Ning began to cultivate according to the method of the Fourth Layer of the Refining Spirit Technique.

And when he finished a round of cultivation and checked the cultivation proficiency in his mind, he was slightly astonished.

[Refining Spirit Technique, Fourth Layer (0/64000)]

"Sixty-four thousand proficiency?"

This was the first time Chu Ning encountered such a high proficiency requirement in his cultivation journey, leaving him momentarily stunned.

He then recalled the proficiency requirements of the first three layers of the Refining Spirit Technique.

"So, the First Layer is 1000, Second Layer is 2 times 2000, Third Layer is 4 times 8000, and the Fourth Layer is 8 times 64000?"

Chu Ning clicked his tongue.

Goodness, he always thought that the amplification of the Divine Sense by the Refining Spirit Technique was quite monstrous.

Unexpectedly, the increase in the level of cultivation difficulty is also so monstrous.

Though feeling a bit overwhelmed, Chu Ning still took out the Six Spirits Pill and Iron Soul Flower.

High proficiency is not a problem, as long as elixirs and spirit medicines can improve, it’s not too big of an issue for Chu Ning.

What Chu Ning needed to determine is how effective these items are at improving proficiency under the obviously more profound Fourth Layer of the Refining Spirit Technique.

A day later, Chu Ning opened his eyes and shook his head slightly.

After several attempts, Chu Ning found that the proficiency improvement of the Fourth Layer of the Refining Spirit Technique is much slower than the Third Layer.

That day he took a Six Spirits Pill and cultivated with the help of the Iron Soul Flower, but after a whole day of cultivation, it barely increased by 2 points of proficiency.

However, upon reflection, Chu Ning thought it was normal.

After all, the Spiritual Sense Strength he has now is comparable to a Golden Core Cultivator.

And even though the Six Spirits Pill, after his refining, had reached Intermediate Upper Grade, it is still meant for Foundation Establishment Cultivators.

This Perfection of the Third Layer of the Refining Spirit Technique did indeed bring a tremendous boost to his Divine Sense.

But correspondingly, the difficulty of subsequent cultivation also increased sharply, which can be considered a happy trouble.

"It seems that to achieve significant improvement in Divine Sense next, it’s necessary to refine advanced elixirs that bolster Divine Sense.

Otherwise, it might take seventy to eighty years to break through this Fourth Layer."

Chu Ning muttered to himself as he started searching through his mind for elixirs that enhance Divine Sense.

Besides the Six Spirits Pill, in the Essentials of Spirit Pill and Jiuhua Sect’s Scripture Room, Chu Ning saw an Intermediate Upper Grade Elixir that can be used to bolster Divine Sense.

It is worth mentioning that both pill formulas noted that they were developed based on ancient formulas of advanced elixirs.

But even so, these two pill formulas are very ancient, dating back six to seven thousand years.

As a result, many of the spirit medicines in them are ones Chu Ning has never even heard of.

"Very likely, during the ancient or medieval periods, the spirit medicines of the Spiritual Sense Type were not as rare as they are now.

If I want to refine them, I still have to adapt these pill formulas according to current spirit medicines."

Improving a pill formula is no easy task.

In his previous work with the Flame Wood Spirit Pill, Chu Ning spent considerable time improving its elixir quality.

And now, although it’s not about improving elixir quality, it is still not easy to find replacement herbs with the same medicinal effect.

Fortunately, Chu Ning possesses the Primordial Pill Spirit Body, having insights into the alchemy technique that far exceed ordinary people.

He has a deeper understanding of the medicinal effects of different spirit medicines in alchemy.

Furthermore, with the experience from creating the Flame Wood Spirit Pill formula, Chu Ning has somewhat explored some experience.

"I have the Iron Soul Flower at hand, which can serve as a very important main herb in the formula.

The rest would have to be figured out slowly."

Thus, for the next period of time, Chu Ning stayed within his Cave Mansion, studying the pill formulas.

A month later, two paper pill formulas lay in front of Chu Ning.

They were the two kinds of Intermediate Upper Grade Elixir formulas that can be used to bolster Divine Sense, which he researched based on Essentials of Spirit Pill and Jiuhua Sect’s formulas.

Chu Ning once considered merging the two pill formulas into one.

But after several considerations, he found significant differences in their pharmaceutics, making complete fusion even more difficult.

So, he simply developed a separate alternative pill formula for each.

Chu Ning didn’t rush into the study of the specific refining method for these two elixirs; first, he had to check if all the various spirit medicines were available.

Thus, Chu Ning casually took out a Communication Talisman, said a few words, and then the Communication Talisman activated and flew out.

Approximately half an hour later, Wang Ping’s voice was heard outside the Cave Mansion.

"Master Chu, I brought the spirit medicines for you."

"Come in!"

At this moment, Chu Ning did not avoid Wang Ping and directly opened the restriction of the Cave Mansion, letting him in. 𝘧𝘳𝘦ℯ𝓌𝘦𝒷𝘯𝑜𝑣𝘦𝓁.𝒸𝘰𝓂

Wang Ping curiously glanced at the two Spirit Beasts, one large and one small, lying outside the Spirit Medicine Garden at the moment.

Then, quickly looked down and walked over to Chu Ning.