It didn't take long for Zhou Fan to make it back to the cave. Once he did, he went to the center of the cave and began to further observe the metal cube.
Its weight was as much as a mountain and not even the strongest weapons of humanity could injure it. In fact, even Xiaolong wouldn't be able to scratch it despite his second level Qi gathering cultivation and the innate strength of the dragon race.
Once Zhou Fan got a good feel of the cube, he was ready to create his most powerful formation yet.
Since there were six sides, Zhou Fan decided to use three for Fire Qi and the other three for Demon Qi.
Zhou Fan coated his finger with Fire Qi. Although he knew that the cube would be much stronger than the previous plates, he wasn't sure how much strength it could hold.
Therefore, he started with one fiftieth of his strength. As he started to carve into the cube, he realized that it could take more, and after a couple more adjustments, Zhoou Fan was able to conclude that the cube could withstand one twentieth of his power.
Any more and it would explode.
With his increased understanding of formations, Zhou Fan was no longer limited to a single line. Instead, he drew patterns that added together and increased the released Qi. After 50 strokes, Zhou Fan was done with the first side.
He repeated his previous actions with the next two sides and switched to Demon Qi on the last three sides.
As he finished the last side, the cube released a glow of crimson red. It had been pushed to its limit and couldn't handle any more formations.
Zhou Fan knew his job was done. All that was left was to test it.
Zhou Fan first started to infuse it with a hundredth of his Qi. Once he realized that it could take that much, he increased the amount to a ninetieth, an eightieth, and so on, until he reached a tenth of his Qi.
At that point it was shaking and light was starting to seep out. When Zhou Fan noticed that it was about to break, he stopped infusing Qi.
As it cooled down, Zhou Fan chose to only infuse a fifteenth of his Qi. Although it could handle a tenth, the stress on it would make it slowly break down.
As he finished testing, Zhou Fan had one more problem. He couldn't always infuse his Qi into it.
Although he estimated that it could work for 2 weeks with his Qi input, it wouldn't work after that and he would have to refill it again.
As he sat there and pondered, his gaze inexplicably turned to the giant crystal hanging from the ceiling. As if a lightbulb went off in his head, Zhou Fan flew to the crystal.
Although he wasn't sure that his idea would work, he had to at least try. Controlling some Sword Qi, Zhou Fan sliced off a chunk of the crystal smaller than his head.
He then carved it into a crystal like shape and began to infuse some of his Qi into it. As he did, the crystal began to emit a soft glow.
He continued to imbue his Qi into it and only stopped after half of it was exhausted. Although full, the crystal wasn't unstable like the cube. Instead, it safely held his Qi within it. Not to mention, there was very little leakage.
He estimated that it would take it thousands of years to expire.
Even so, the current revelation was good for Zhou Fan. With these crystals, there would always be Qi to refill the formation on the cube.
While looking at it, Zhou Fan decided to call it a spirit stone. The name seemed like a good fit.
After he was done with the first, Zhou Fan continued to cut down the crystal in the middle and shape it into spirit stones. He only stopped once he used up half of the crystal and created 1000 spirit stones.
With these, the formation would be powered up for 2000 weeks, or 38 and a half years.
Zhou Fan had fulfilled his promise to Cao Lin. Speaking of Cao Lin, Zhou Fan called him over.
After showing him the cube and explaining its functions, Cao Lin was amazed. He then explained the use of the spirit stones and taught Cao Lin how to use them.
"Uhhh sir. Couldn't you just fill up the spirit stones and let me cultivate with them?" Cao Lin asked.
Hearing his question, Zhou Fan stood rooted to the ground, frozen. He had never even thought of that. After all, he had only discovered spirit stone after he had already completed the formation.
As Cao Lin stared at the frozen Zhou Fan, he let out a small chuckle. Even the almighty make mistakes.
It took a good minute before Zhou Fan unfroze.
"Well you could, but the spirit stones contain neutral Qi and the Demon and Fire Qi produced by the cube would be much more beneficial." Although he could have just filled up the spirit stones with Fire and Demon Qi, Zhou Fan didn't want to admit his mistakes.
"Oh. Of course sir. How could you make such a simple mistake." He said with a smirk and a sarcastic bow.
Seeing that, Zhou Fan had to stop himself from sending Cao Lin flying into the next life.
When Cao Lin saw Zhou Fan's expression, he turned around and ran. By the time Zhou Fan started to pay attention to his surroundings again, he was already gone.
"Good, very good." Zhou Fan muttered with an evil smile while rubbing his hands.
All that he needed now was a long mustache and he could be a villain.
Since he was done with formations for now, Zhou Fan pondered what else he needed to do. After seeing the possibilities of formations, he wondered if there were any other special uses for Qi besides cultivating.