The 8th-grade Mortal Warrior stage was simple enough to summarize. It was called Qi Impact. The cultivator had to throw each crystallized Dantian against each other so they would merge together in a cataclysmic explosion. The crystallized Dantian were, to be more accurate, the crystallized Qi within the Middle and Lower Dantian. Indeed, the Dantian themselves could not move, it would be like moving one's heart within their body. But the entire Qi contained in both Dantian that had turned into small crystal with immensely dense energy within were called crystallized Dantian themselves by extension.
In principle, it was easy. In practice, it was incredibly risky and difficult. Indeed, first of all, the two crystallized Dantian had to be appropriate for each other. Thankfully, Cao Yun had succeeded in this endeavor as much as he possibly could. It would be difficult for anyone to reach a more suited state for both of their Dantian. What really mattered wasn't necessarily the stat of each one, but their relation to each other. Cao Yu had almost reached a perfect state for both of his Dantian. Thus, he could begin this next phase with a serene mind. And this was the most important part.
First of all, both crystallized Dantian had to be thrown at each other with the right amount of strength so they would meet around the Huang Ting, the Yellow Court. This acupoint was near the stomach, but the name was also used to describe the entire region. The two crystallized Dantian would be thrown along the axis of the Ren Mai, the Conception Vessel that also connected the three Dantian from the front of the body.
If the impact took place too close to either Dantian, it could shatter them, either leaving heavy injuries, crippling the cultivator, or even killing them on the spot. So aiming for the right place was essential.
At the same time, they had to be thrown with as much strength as possible while the cultivator had already sealed most of their Qi within the two crystallized Dantian precisely. So they had to rely on their will and intent to command them. Hence, it was essential to have a great control over one's Qi. For that part, Cao Yun had no worry at all. But he was worried to throw to hard or too soft. Indeed, the two crystallized Dantian had to explode upon impact so their energies could merge together and give birth to the Soul Embryo.
If the impact was too weak, they would not shatter but they would be damaged. In which case, the cultivator either had to attempt to do so again, risking to birth a weak or deformed Soul Embryo. Or they would have to get both crystallized Dantian back in their original Dantian to break them apart and attempt the breakthrough another time. Once again, reverting the crystallized Dantian back into Qi was not an easy process and it would bring about some consequences for the cultivator.
On the other hand, if the cultivator threw them too hard, the shock could injure them. It was why the Extraordinary Vessels had to be sturdy enough to resist it. In theory, the stronger the impact was, the better things would be. But the Extraordinary Vessels had to resist it. Moreover, the impact shouldn't be too strong either as to not send a feedback into the two Dantian that were obviously connected by the Conception Vessel.
Cao Yun first began to move around each crystallized Dantian to get a feel of how they behaved. Even though he had read that in Cleansed Asura's documents, he would have thought about it by himself. And this was the right move. Indeed, in this new form, Qi behaved quite differently and Cao Yun would have to take that into consideration. As such, he played around with both crystals for quite some time. He even moved them outside of his Dantian to get the right sensation. But he was extremely cautious as to never get them close to one another.
Once he was comfortable moving them around, he did approach one with the other. Immediately he felt both an attraction and a repulsion. The Water and the Fire elements were pushing each other away while the tiny amount of the other element was getting attracted. In other words, the Water Qi attracted the Water Qi but repulsed the Fire Qi and vice versa. That meant that he would need a lot of strength to pulverize them against each other. Slowly, he tried to get them as close as he could to understand how this force between them would react. The closer they were, the stronger this repulsion was. It was to the point that it would have been impossible for Cao Yun with all his strength to make them touch each other. Thus, it was imperative to throw them toward each other so that the momentum itself would break this intangible barrier.
Finally, Cao Yun decided to attempt the Qi Impact. Beforehand, he summoned all the vitality of the world tree within him. In his body, it felt as though vines were growing all around his Conception Vessel, but only in the segment between his Lower and Middle Dantian. Although the young man wasn't too afraid about damaging his Middle Dantian thanks to the Drop of Wrath, he was sincerely worried about his Lower Dantian. Thus, he focused a large part of that vitality around his Lower Dantian. Technically, it was stronger as he had tempered it for much longer. But the protection of the Drop of Wrath made the Middle Dantian even more resilient.
Of course, Cao Yun was also using his blood and the property of the Drop of Wrath within to protect his Lower Dantian, but he preferred to be as cautious as possible.
In his mind, he knew that the collision would happen almost instantly after he would throw the two crystallized Dantian. After all, the distance was quite short and he would need to throw them with unimaginable speed. In other words, he would have almost no time to protect his Dantian between the moment he would throw the two crystallized Dantian and the moment they would collide. So he prepared as much as he could to be ready when that happened.
At last, after more than two weeks, Cao Yun was as ready as he could get. Of course, he could always try to prepare more. But at this point, he would only waste time. Considering that most of his Qi was condensed into two crystals, he couldn't waste all the time in the world. He had to act before this absence of energy affected him.
Nothing existed in the world but his two crystallized Dantian. Cao Yun didn't even focus on his Extraordinary Vessels now that he had prepared them. He was confident in his training until now and knew that they would resist almost anything he could throw at them. What he wanted now was to get the best impact possible between the two crystallized Dantian. Once thrown, there was no coming back. But the young man was resolute.
Suddenly, the two small crystals were thrown against each other by an invisible force that was Cao Yun's spiritual senses. Even Mortal Warriors who didn't have spiritual senses could do so. Indeed, they could move their soul around within their own body, but unlike Cao Yun, they couldn't move it outside of their body. That being said, because Cao Yun had reached genuine spiritual senses, they were thus stronger even within his body compared with other Mortal Warriors. As such, the speed exceeded what any other Mortal Warrior could have achieved. Which was both a good and a bad thing, it all depended on what Cao Yun could support.
In the blink of an eye, the two crystals collided against each other. As soon as they did, they ruptured completely. The crystals were shattered into countless tiny shards that kept on colliding against each other. They were thrown everywhere within Cao Yun's Conception Vessels. It didn't take long but it felt like an eternity for Cao Yun who was using his Chamber of Heavenly Court. The shards became smaller and smaller. Soon some completely exploded and reverted back into pure Qi.
His Conception Vessel was bloated but it endured. The vitality of the world tree sustained it and his blood nourished it as it was under attack from within. A few small injuries were caused by the large explosion but thankfully they were healed almost instantly. And almost nothing injured his Dantian. However, he could feel an incredible force and heat within his Yellow Court. It felt as though he had swallowed a small sun. That being said, he had known worse when he had been into the Blood Abyss. The pain was probably unbearable for many but not for Cao Yun, not even when it had reached this level.
Before it could calm down, Cao Yun had to enter the final stage, the 9th-grade Mortal Warrior stage. It was called Embryo Formation. Once again, the name was self-explanatory. This last stage was difficult because it had to be performed right after the collision of the two Dantian. Under the force of the impact, Water Qi and Fire Qi were able to merge with each other to produce something completely different. Cao Yun realized that this new substance was akin to his very own soul, but also slightly different. This substance was the foundation of one's Soul Embryo. But simply leaving the wild Water Qi and Fire Qi act out wasn't good enough. Now that he had been able to break the barrier between these two elements, he had to manipulate them so he could form his own Soul Embryo.
This stage was almost impossible to interrupt. Indeed, the two forms of Qi were mixing with each other. Even if the cultivator did nothing, some kind of Soul Embryo would be born. And once it was born, there was no altering its foundation. Of course, even a weak or deformed Soul Embryo could be useful as one would still temper and nurture it. But its foundation was exactly what prenatal Jing was to humans and demons. It was possible to refine and temper it but almost impossible to really improve it. In fact, the Soul Embryo's foundation was even harder to alter. The only pill Cao Yun knew about that could do so was a 5-star God pill. And he had learned about it while reading Cleansed Asura's document. No one in the Hongchen Kingdom had ever heard about such a pill. And no one probably would, ever.
The difficulty of this last stage resided in the control of the two elements. Fire and Water were behaving in a completely new way. Even Cao Yun's knowledge as an alchemist couldn't prepare him for this. The state of those two elements was never encountered in nature. Maybe it was similar to how a soul was born when two parents shared their Jing. But it was also slightly different in ways difficult to describe. Even Cao Yun who had read extensively on the matter and was feeling it at the moment could not fully understand nor describe what was happening. The two elements were both behaving as usual while breaking every law and notion he had about them. Indeed, they were both Water and Fire and something else in-between at the same time. That substance was more primitive and raw, but it still contained traces of both elements. At the same time, it had traces of other elements.
As much as the two crystallized Dantian had been purified, there were always traces of the Five Elements in all things.
Using his entire knowledge of alchemy, even texts from Cleansed Asura, Cao Yun did everything he could to control the process. His goal was simple enough. He had to make sure that the Fire and the Water merged as much as they could into this new substance so as little of the original elements were present within his Soul Embryo. And he could literally feel his Soul Embryo being born while doing so.
Alchemists had a bit of an advantage. But even Cao Yun had a hard time so this advantage didn't amount to much. Besides, Cao Yun also a vast understanding of array formations. It helped him as well, but didn't amount to much either.
Nothing he had read could really prepare him for this last stage. It was incredibly personal and was different for each cultivator. This was the last step to break through the barrier between Mortal Warrior and Spirit Warrior, the last part of the Lesser Tribulation. Although Cao Yun had crossed through the most dangerous part, this last part would shape his future. If his Soul Embryo wasn't good enough, he wouldn't be able to reach the highest levels of cultivation. And short of dying and being reincarnated, there was nothing to do to improve the foundation of one's Soul Embryo. Even the pill he had read about was unreachable. After all, Cleansed Asura himself would have been unable to get one.
Doing everything he could, Cao Yun tried to control this wild energy and to focus it where the Soul Embryo was being formed. At first, it was a small ball of silver, but it kept on growing and growing. Slowly, its shape changed and looked more and more like a small human, a silver baby in a fetal position.
As time passed, the wild energy calmed down. More and more of it reverted back to pure Qi. Thus, Cao Yun got more and more anxious about merging what wild energy remained with his Soul Embryo. However, he remained as calm and composed as he could despite his hurry. He didn't want to risk damaged this forming Soul Embryo.
Finally, everything calmed down within Cao Yun's body. Then, something gushed forth from the tiny silver baby that seemed to sleep into his stomach. A powerful silver light shined and drowned his entire world. Even his sea of consciousness became full of this silver color. Nothing else existed. Cao Yun had officially entered into the Spirit Warrior Realm, also known as the Embryo Realm.
When he opened his eyes next, he was floating above the ground and his soul was naturally spread all around him. Although the change wasn't much because he had already had this experience before, emotionally, it was powerful. After all, he had reached the realm his father had attained just before his death.