Cao Yun immediately entered his inner world. Although his martial arts were stagnating a bit, he was just too focused on the study of the Dao for the moment. Unfortunately, he was clearly hitting a wall. The current methods he was using were progressing increasingly slowly. At the same time, he had difficulty understanding the higher methods.
When it came to his Dao of Death, he was slowly getting the hang of 'Macabre Dance'. Indeed, he was able to animate a small skeleton. For the moment, he was still forced to manage them himself, but he was starting to give simple commands. The bird skeletons were able to walk unassisted but couldn't do anything too complicated. Besides, they couldn't fly since they were just bones. Using Death Energy, it should theoretically be possible for them to actually fly, but it would consume so much of it that the bones would collapse. Unless Cao Yun could restore the tissues, the skeletons were very limited. As such, he would have to try on actual bodies that had not yet turned into bones. However, it was harder.
After 'Macabre Dance', 'Death Verses' talked about five more methods. The next one was 'Death Elegy'. Honestly, Cao Yun wasn't even sure how to tackle this or what it was supposed to be precisely. Apparently, it was about going against life itself, but it didn't seem to use Death Energy. This was the very first method of 'Death Verses' that only used the Dao of Death without a medium like Death Energy or Evil Qi. If Cao Yun's understanding of death wasn't good enough, he simply couldn't practice it at all. Unfortunately, there weren't many places where Cao Yun could study the Dao of Death on the Piaolu planet. And he wouldn't create his own mass grave to study death. After all, he would probably need to kill tens of thousands of people, even more than that, to have a chance to catch a glimpse of the Dao of Death through the corpses.
The following method was 'Life Through Death', then 'Death Through Life'. Both of those actually involved Death Energy but in completely different ways, and through the Dao of Death as well. From what he understood, both methods required the ability to turn Po into Death Energy and Death Energy into Po. In other words, it was about turning life into death and death into life. Cao Yun knew how to do it to his own Po, but only if he didn't go all the way. First of all, if he were to actually die, he couldn't revert back to life. More importantly, he couldn't do it to others. If someone's Po had begun to turn into Death Energy, Cao Yun had no way of even stopping the phenomenon, let alone reversing it.
Anyway, just like the Dao of Fire, Cao Yun had ideas on how to better understand it. But it could only happen in the Withering Fusang Domains. Moreover, this wouldn't be as easy as the Dao of Fire, not according to Emperor Nuwa's journals.
When it came to his Dao of Fire, he focused on Fire Silk, Tyrannical Flame, and Heatless Flame. Unfortunately, the next method, Ten Thousand Candles, was much more complex. According to Red Calm, one who mastered it could claim to have just entered Dao Growth. Ten Thousand Candles was about creating independent flames. They had to be many, but they also had to be able to act without the cultivator's command. In a sense, it was similar to what Cao Yun was trying to do with the skeletons. The flames had to be able to act through the will of the cultivator without explicit commands. They wouldn't be sentient or anything, but those flames would simply be an extension of the cultivator's will. Obviously, it was incredibly difficult.
Thankfully, his cultivation was progressing at a steady pace. In fact, his asura cultivation was even starting to become boring. Even now, he was still sending his Common People's Fire from his bladder into his lower abdomen to fill it up completely. Since asura didn't have a Lower Dantian, this gave Cao Yun surprising results. Not only did it strengthen his flesh, blood, and even essence like any other asura, but it also strengthened his Lower Dantian and by extension his Qi. His Golden Blood was much stronger, and his prenatal Jing was richer and denser than ever. Although he couldn't increase the amount of prenatal Jing, he was barely using any when converting it into Qi. In other words, his vitality was exceptional.
Despite all those benefits, there was nothing to it anymore. Cao Yun simply had to permeate his entire lower abdomen with this Common People's Fire while progressing upward. Slowly, the reddish-violet hue began to turn. One day, Cao Yun realized that his lower abdomen simply couldn't take any more Common People's Fire. All the Common People's Fire he was pouring into his body began to simply pour out of his back. In his Mingmen, Cao Yun could feel intense heat. Besides, the reddish-violet hue of the flame became a dark blue, or indigo. Those were all the signs that Cao Yun had achieved a breakthrough. Honestly, he had not even noticed it. However, there was no doubt.
At this moment, Cao Yun realized that he was a 3rd-grade Exalted Demon. Now, he had to make his Common People's Fire penetrate his lower back. This wasn't as easy as it seemed. Indeed, his lower abdomen was already full of it and couldn't take any more flame. As such, the pressure was intense. But Cao Yun had to pour the Common People's Fire inside his lower back without losing it and without damaging his Mingmen since it would be essential in the next grade. He might not achieve it before leaving seclusion, but it would be very close.
Regarding his human cultivation, Cao Yun spent ten more years on the foundation of his inner pagoda. One day, he sensed a powerful force and a blinding white light spread throughout his inner world. At last, the first floor of his inner pagoda was complete. For the first time ever, Cao Yun could enter it. It was exactly the architecture Cao Yun knew from the Hongchen Kingdom. At least, it looked like it at first. Examining it more closely, Cao Yun realized that some details reminded him of asura architecture, but even other forms of architecture he had seen through Cleansed Asura and Axiu Qian's memories. However, the dominating influence was from the Hongchen Kingdom. Obviously, Cao Yun knew that his inner pagoda was the manifestation of his soul. As such, it would necessarily be based on his perception of what a pagoda was.
In the center of the first floor, there was a large pillar supporting the roof. Later on, this roof would become the second floor. Although the pagoda had only one floor now, it was tall enough to accommodate someone five times taller than Cao Yun. The final pagoda with nine floors would be gigantic. That being said, Cao Yun knew that there were taller pagodas in real life. Of course, his pagoda had no actual reason to follow the laws of the real world.
Sadly, the first floor was quite empty. This was the only floor of the inner pagoda that didn't rely on any treasure as a foundation. Indeed, the foundation of the first floor was the sea of consciousness and the Soul Embryo. From now on, though, Cao Yun could absorb a treasure as the foundation of any additional floor. This wasn't compulsory, but there was no reason not to do so if a suitable treasure was found. However, putting in a treasure that wasn't compatible with a floor was generally a terrible idea. Thankfully, Cao Yun already had a few ideas, but most treasures were in the Withering Fusang Domains.
In fact, there was only one treasure that Cao Yun could access at the moment.
Each floor of the inner pagoda was related to a specific symbol that would subsequently alter the inner world, but also be connected to a part of the cultivator. For the second floor, the symbol was the Tree, and it was connected to the physical body of the cultivator, his flesh, bones, and muscles. For a short moment, Cao Yun had imagined that he could use the Withering Fusang Tree, but it would take a long time before he could accomplish something like that. Thankfully, he had an even stronger tree, the world tree Cleansed Asura had encountered. At this very moment, Cao Yun had a seed of the world tree with roots everywhere within him.
For his second floor, Cao Yun intended to simply use the world tree. As a matter of fact, Cao Yun remembered the Yellow Death World. The Yellow Death World was Cleansed Asura's inner world that had collapsed. Inside this world, Cao Yun had found his inner pagoda. And it was on the second floor of this pagoda that he had found the world tree and obtained the seed of the world tree. Cao Yun had absolutely no reason not to follow the example of Cleansed Asura. This second floor would be the world tree.
With immense patience, Cao Yun spent weeks spreading his intent throughout his body to immerse himself within the roots of the world tree. At some point, he couldn't even feel his body anymore, he only felt the tree. Cao Yun was the tree, or rather the seed. He could feel that the seed was ready to sprout. It was just waiting for the right soil. While leaving the roots in himself, Cao Yun slowly moved the seed itself into his inner world. After months of hard work, the second floor of the pagoda began to appear, but it was fading in and out of existence. Within the second floor was the seed of the world tree.
Now that the second floor had a foundation, Cao Yun had to work on it in order to fully materialize the second floor. This wasn't easy at all, but the presence of the world tree made it less difficult than it could have been. In fact, Cao Yun quickly realized that the seed was now ready to open and bloom. Maybe it was because its parent had literally been inside Cleansed Asura's inner pagoda, but this was the perfect environment for the seed. Besides, this wasn't a manifestation of the seed. No, this was the actual physical seed inside Cao Yun's soul.
Usually, spatial rings couldn't contain life, and neither could inner worlds. At least, Sages couldn't maintain life within their inner worlds because their inner worlds were still too unstable. Everything that seemed alive was, in fact, a manifestation of one's soul. However, the world tree was different. By keeping the roots of the seed within Cao Yun's body and the seed inside his soul, which had been quite delicate, Cao Yun could fully keep it alive. The seed of the world tree was already forming a form of domain around itself. Killing it, by any means, would be extremely difficult. At most, Cao Yun could probably just make it dormant, but he would have a hard time actually killing it, which was a good thing, actually.
After less than five years, the seed finally opened, and a tiny growth appeared. Slowly, it was growing and growing. Within Cao Yun's memories, the image of a tree so large that it had taken over an entire planet and had become the planet itself was still vivid. This world tree was another great treasure that Cleansed Asura had left to Cao Yun after his death.
Maybe Cao Yun was strong enough to go underground and get his master's corpse. At least, he hoped so because he wanted to properly deal with Cleansed Asura's corpse before he left the Piaolu planet. Cleansed Asura had wanted to be cremated, and Cao Yun intended to respect his dying wishes. Unfortunately, even Matriarch Huang Yufeng had failed to recover the body. Hopefully, Cao Yun could succeed after this seclusion, but he wasn't completely sure of it.
Finally, after around fifteen more years, Cao Yun could claim that his second floor was complete. It was now as concrete and physical as the first floor. When he entered the second floor, Cao Yun found himself in a vast green plain, almost like his own inner world. However, this wasn't infinite at all. Cao Yun could clearly sense the walls of the pagoda even though he couldn't see them without focusing on them. This was different from Cleansed Asura's second floor. To be fair, the world tree was tiny, not even reaching Cao Yun's hips, but still taller than his knees.
Outside his pagoda, Cao Yun could now see a tall tree. It didn't look like the world tree at all. No, this was the manifestation of the second floor. Now, his inner world was slightly different. Cao Yun could feel that it was stronger. As the tree grew, his inner world would also become stronger and stronger.
The third floor of the inner pagoda was related to the symbol of the Pillar, similar to the tree in a way, but also different. For Cao Yun's body, it was the representation of his Extraordinary Vessels. In particular, the Pillar was referring to the vessels connecting the three Dantian together. Qi would flow with much more power, creating a pillar of strength for the cultivator.
Unfortunately, Cao Yun had no way of accessing the treasure he had in mind. Indeed, no treasure on the Piaolu planet had caught his eye. What he wanted was something that could only be found in one of the Withering Fusang Domains. At least, he didn't know of anywhere he could go where such a treasure could be found. Besides, it was almost impossible to change a treasure once it had been used as the foundation of a floor. After all, Cao Yun would have to tear up the entire floor. Rebuilding the inner pagoda was extremely difficult, nigh impossible. Even if one succeeded, the inner pagoda would be weaker and could literally collapse on its own.
Anyway, it was soon time for Cao Yun to leave his seclusion. Although he couldn't tell how long he had spent in his seclusion, he could guess. Indeed, he was on the verge of becoming a 4th-grade Exalted Demon.
As a matter of fact, this was what Cao Yun focused on during the last months he remained in seclusion. His lower abdomen and lower back were filled with his Common People's Fire, which was about to spill over.