Doctor Mo did not have many happy days. The Mortality Decimation Curse revealed its deadly side effects, causing him to age at the rate of one year for every passing day.
He was terrified at the rate he was aging and tried everything to find a way to control the abnormal effects of the curse, but there was little to no success.
He knew that if this continued on, he would not live for much longer, as his body would begin to fail him and he would eventually die like any other old man. Yu Zhitong, on the other hand, was in even more pain. When his soul entered Doctor Mo's body, it was slowly but painfully being assimilated into Doctor Mo's soul.
Assimilation, a passive event, would occur if one's soul remained in a foreign body for a prolonged period of time. Since one body can contain only one consciousness, the stronger soul would try to subdue the weaker soul, thus beginning the long process of assimilation.
Yu Zhitong decided out of desperation to reveal everything he knew concerning why they wanted Han Li's body. He was reluctant to do so not because he was good at heart loyal to Doctor Mo but rather because he was fearful of the the cultivation world's Three Big Inviolable Rules.
First, cultivators must not forcefully possess the bodies of normal mortals as they were unable to withstand the immense amount of stress, causing the body to ultimately burn out.
Second, only those with greater;magic power;will be able to successfully overtake the body of a cultivator with weaker magic power;and not suffer from any form of counterattack. The greater the disparity between the levels of power, the safer it would be for the the one attempting the possession.
Third, a cultivator is only able to perform body possession once in his entire life, no matter how powerful their magic power;is. If they were to attempt to perform body possession a second time, their soul will perish without fail.
Although the number of people who tried to break the three rules is unknown, the Three Big Inviolable Rules have never been broken. These three;rules limited countless evil cultivators who tried to use the body possession technique and prevented them from creating calamity in the mortal world. The Heavens frowned upon actions that go against Heaven's Will because no matter what, the Heavens would not allow cultivators to throw the world into chaos.
If Doctor Mo had been a cultivator, Yu Zhitong would not be in his current predicament as he would have had a viable chance at possessing Doctor Mo's body but since Doctor Mo was a normal mortal without a hint of Spiritual Qi, there was no way for Yu Zhitong to possess his body for fear that halfway through the possession, Doctor Mo's body would be unable to handle the stress and ultimately break down.
Even if Yu Zhitong was able to find another body to possess, the process of assimilation was inevitable and he might fall under a more dire predicament as every time he leaves and enters a new body, he loses a bit of his Spiritual Qi, which will quickly be expended. When this happens, Yu Zhitong will no longer be able to enter and exit someone's body at will and may even be indefinitely stuck in someone's body and ultimately be assimilated.
It is also important to note that without a body, he was unable to replenish his;magic power;through meditation, so every time he used magic power;it was lost forever. At the same time, his magic power;also leaked out at a slow but steady pace and even he didn't know how long his soul could maintain its current form.
So unless Yu Zhitong found a cultivator capable of using small amounts of;magic power;and had a body capable of withstanding possession,he would not take any risks and leave his current body, which was that of Doctor Mo.
Just when Doctor Mo's body was about breakdown because of the blood curse, the aftermath would leave Yu Zitong's soul without a body to lodge in.
After the collapse of Doctor Mo's body under the blood curse, leaving him without a body to return to, and the fact that Han Li may consume his remaining life force, Yu Zhitong decided to temporarily place aside his hatred and give Han Li anything he wanted, even going as far as betraying Doctor Mo, revealing how they met and their plans, along with the stakes and benefits involved, without holding anything back.
When Doctor Mo first heard of Yu Zhitong's plan for revitalizing his body, it made him express anger, but he quickly realized that this was a perfect opportunity and quickly pledged to achieve their goal, revealing him to be a man of dignity.
First, Doctor Mo must follow Yu Zhitong's instructions and control his consciousness so that it does not assimilate his soul. Yu Zhitong also taught Doctor Mo a few secret techniques that allowed him to slow down the rate of aging he suffered from his curse while also temporarily allowing him to use magic power.
Then Doctor Mo must find someone with strong spiritual roots who was also able to practice the Eternal Spring Arts, teach him the incantation and then wait for when the time was right before Doctor Mo used his temporarily gained abilities to use magic power;to forcefully take over the other person's body in order to start a new life.
Doctor Mo's sincere desire to traverse the path of cultivation was ridiculed constantly by Yu Zhitong since he knew firsthand how impossible it was for normal mortals to use magic power. Doctor Mo was merely a;mortal cultivator of the mouth with no spiritual roots in his body. (TL: "cultivator of the mouth" means he only talks about cultivating without actually doing it.)
After Doctor Mo succeeded in overtaking a body with spiritual roots and had sufficient time to rest he would then proceed to help Yu Zhitong find a suitable body to possess and then provide any aid to help Yu Zhitong possess his new body.
From the conditions above it seems like Doctor Mo receives the most benefits from this deal, but that couldn't be helped since Yu Zhitong was caught in a bad position with his remaining soul force under constant threat of assimilation. In the end, Yu Zhitong was forced to accept this unfavorable agreement and take a bit of loss. However, it was not clear if he really was taking a loss; after all, the only person who knew the exact terms of the agreement was himself.
At one point, Yu Zhitong suggested that Doctor Mo should go back to his family and ask for help, but the rapidly aging man refused to even consider that option, much to Yu Zhitong's constant annoyance.
What came afterwards didn't warrant much discussion as Doctor Mo spent most of his time trying unsuccessfully to look for a suitable body and reluctantly entered the Seven Mysteries Sect, where he accepted Han Li as a disciple and taught him the Eternal Spring Arts. The rest that occurred was not worth mentioning as they were either mentioned by Doctor Mo himself or was experienced by Han Li himself.
After Han Li finished hearing those words, he let out a long sigh as some of the confusions and questions within his heart were answered by Yu Zhitong. Seeing how Yu Zhitong did not continue, Han Li's face grew darker and he coldly said, "It seems you still haven't told me how Doctor Mo died."
Yu Zhitong hesitantly opened his mouth and said "Is there else worth explaining? Doctor Mo underestimated your cultivation speed of the Eternal Spring Arts and his magic power;was not as strong as yours, so therefore he was unable to take over your body, resulting in his soul being devoured."
"So, the yellow ball of light that first entered my body was Doctor Mo and the second green ball of light was you," Han Li stated calmly, almost as if the invasion of his body had not been a big deal.
"Well... about this, at that time I thought that both you and Doctor Mo were exhausted and I did not want to waste this opportunity and so I thought I might borrow your body for a bit," Yu Zhitong replied awkwardly.
"Heng! I'm afraid that's not the reason why you attacked. I think that you had it all planned out from the beginning."
"Yu Zhitong, I bet that when you were first explained the process of body possession to Doctor Mo, you didn't have any good intentions and therefore didn't bother to mention that the success rate of body possession was directly correlated to the strength difference.
"Do you know what I think? I think that you had it all planned out from the beginning. You made Doctor Mo use the self-mutilating Seven Soul Devouring Technique against my fourth level cultivation of the Eternal Spring Arts, which are near equal in terms of power, so that we would both become exhausted to the point of perishing together. After the battle came to a draw, you would then step in and reap the benefits of Doctor Mo's painstaking work and ultimately take over my body. Did I guess correctly, Cultivator Yu?" Han Li calmly stated his assumptions in the time it takes for several breaths.
After a long moment of silence, Yu Zhitong let out a sigh expressing his dejection. Without refuting, he said "I originally wanted to give you empty praises but now I sincerely mean it when I say that you are extraordinarily smart, even outshining your master Mo Juren, that cunning fox."
"You guessed correctly. All of this was planned out by me, but I never would have thought that your talent for cultivation was so high that you would train up to the sixth layer of the Eternal Spring Arts, only one layer below me, in such a short period of time. Not only did you easily swallow Doctor Mo's soul, but my heavily depleted soul force was not even a match for you and I even lost a large portion of my soul to you."
Once finished, his tone suddenly turned prideful "Ha! That Mo Juren was only a normal mortal yet he wanted to stand on equal footing with us cultivators. Was he even worthy?
"Moreover he dared use such despicable means as to get rid of my cultivating body and still wanted to step onto the path of cultivation! He was simply daydreaming!" The hatred Yu Zhitong had kept bottled in his heart for a long time finally revealed itself.
"But you are different, you were born with spiritual roots and intelligence above the norm. Staying in the secular world would be too much of a pity! If you are willing to help me find a new and suitable body, I am willing to act as your guide, introduce you to the elders of my clan, and accept you as my disciple. What do you think?"