Lin Mu laid in the sand pit, while his Immortal Sense spread over it and went underground.

He was observing it in detail, wondering how the First Form of the boulder Collapsing Fist had affected it. At first Lin Mu had thought that the skill directly pulverized everything and turned the rocks and stones into sand.

But now that he was observing it deeply, he noticed that there was actually a gradient to it all.

'The size of the particles actually varies…' Lin Mu noticed that the particles at the very top of the surface were big, having cracked roughly. These were also the stones that had pelted him during the initial impact.

After this was the finely pulverized rocks and stones, that had turned into sand. This was the majority of the area and only when Lin Mu went to the deepest part did he noticed the particles getting bigger again.

'Hmm… so the first meter of depth is only cracked but after that the coming parts are directly pulverized. Only the final few meters that are affected by the skills are left bigger, but even then they are still broken.' Lin Mu concluded.

Over all, he could see that 1% of the affected area was left in chunks, 94% was turned into sand while the last 5% was left as bigger particles like gravel.

Having learned all this, Lin Mu now wondered how it related with the consumption of the Immortal Essence.

'Now to try it with varying consumptions…' Lin Mu began the process again.

But this time, he increased the number of Immortal Essence wisps that he used. Instead of ten wisps, he used fifteen wisps!

This made him take longer to prepare the skill, but it was still something he could manage to execute. And when he was finally ready, he punched the ground again.

~KABOOM~

Another sand pit was created by Lin Mu and he quickly got to analyzing it.

What he learned this time though was a bit different.

"The area of the sand pit has increased and so has its depth…" Lin Mu muttered to himself.

If before the area affected was a hundred meters in radius and hundred meters deep, now it was hundred and fifty meters in radius and equally deep.

'The area of effect is in the form of a hemisphere, I see…' Lin Mu noted.

Having observed this, Lin Mu began the process again, but this time he reduced the number of Immortal Essence wisps used. He used five Immortal Essence wisps, finding it a lot faster to be prepared.

~BOOM~

And once the skill was ready, he executed it once more, creating another sand pit.

"Just as I thought… the sand pit is half the original size." Lin Mu said to himself.

The sand pit created this time was just fifty meters in radius and equally deep with the particle size gradient changing proportionally.

'So each wisp of Immortal Essence adds about ten meters of area that will be affected.' Lin Mu understood.

He continued his series of tests and spent a couple of days in this.

After he was done with it though, he had learned a few more facts about it. The first thing he learned was his new limits with the immortal Essence.

The first limit was on the number of Immortal Essence wisps he could use.

Lin Mu found out that he could use twenty Immortal Essence wisps at the maximum before he would be unable to even activate Boulder Collapsing Fist. If he went even a single wisp over that limit, the spiral would become unstable and all wisps would dissipate violently.Published by Nôv'elD/rama.Org.

The only time Lin Mu had done that, he had damaged his arm internally. Thankfully he could also heal it quickly due to his higher body cultivation base.

The second thing he learned was the time needed to prepare the skill also varied. The more Immortal Essence Wisps he added to his arm, the longer it would take. The shortest time was needed with three Immortal Essence wisps, needing only a minute to prepare.

Three immortal essence wisps was also the minimum number to use the first form of the boulder collapsing fist. If he went any lower, the skill simply wouldn't be able to activate as the spiral wouldn't be big enough.

As for the upper limit of the number of wisps, Lin Mu reckoned that it was only his control that was limiting him.

'Theoretically if I can improve my control over the Immortal Essence wisps, there shouldn't be a limit on the maximum I can add. It is merely my body that is not adapted to it which should be fixed when my body cultivation base improves.' Lin Mu reckoned.

The Seventh Stage of the Three Apertures Invoking technique, the Aperture Closing stage was when a cultivator's body would fully adapt to the Immortal Essence. At that point, they would have no need for the apertures and would be able to directly utilize the Immortal Essence and store it within their body.

'But simply increasing my body cultivation by a stage or two, should still increase the upper limit of the number of Immortal Essence wisps I can use.' Lin Mu understood.

The next thing that Lin Mu thought of was, how he could optimize the boulder collapsing fist.

"If I want to use it in battle, I need to shorten the time needed to prepare it…" Lin Mu muttered to himself.

And in order to do that, there was only one method.

"I need to practice more!" Lin Mu said with determination.

He returned to his training and used the skill over and over again, trying to improve his control over the Immortal Essence wisps and reducing the time needed to form the spiral for execution.

Hours tuned into days as Lin Mu was soon lost in practice.

Thankfully, there was still Little Shrubby who could continue the search for the immortal stone mine. Lin Mu had assigned the task to the beast for now, as there wasn't many areas left to search anyways.