Sole Cloud Flying Cave

Cui Heng was transmigrated to another world and the system told him that the new world he was in was a high-grade Xianxia world.
It was a world where Celestial Kings soared the sky and terrifying monsters ruled the lands. The strong would destroy a planet if their mood was bad and Cui Heng trembled in fear when he learned of how scary the new world was.
Thankfully, the system had granted him the protection that last for 300 years. As long as he remained in the safety zone, he would not receive any damage.
With his safety secured, he began his cultivation training for the next 300 years.
Throughout the years as he trained, some people entered his safety zone by mistake.
There was a peasant who was once a monk and a beggar. Despite that, he still had the dream of bringing peace to the land and saving the lives of millions.
There was a noble who was once called the once-in-a-million-year genius. Yet, luck wasn't at his side and his talent fell and was laughed at by others for years.
There was a princess whose only wish was to find her older brother. She could've become a celestial but decided to remain in the human realm to wait for her brother's return.
There was a weak lady who was plagued with illness from birth but had the goal of adventuring and helping the poor and weak.
...
Cui Heng befriended these people and even gave them a few pointers before they left.
300 years later, when the protection period had ended, he had finally mastered the Golden Core. Even then, he was still reluctant to go to the outside world.
But when he did, he realized that the world was merely a world of Wuxia.

Realizing This Is A Wuxia World After Cultivating For 300 Years

<p>In that case, I only need to wait. When the reincarnation of the spirit reaches a certain realm, he will naturally seek a higher level and come into contact with the path to this universe. At that time, I felt that I only needed to wait here. After all, that's only the reincarnation of Existence's spirit. It's impossible for him to be my match. So, what went wrong with this entire process? There shouldn't be a problem. Why didn't he fuse with the aura of power left there? And how did he become so powerful? He's just a reincarnation of a spirit that doesn't have the power of 'form' to support him, so he shouldn't be powerful to this extent.</p>

<p>"Even the 'Foundation of Existence' that fused with the body and spirit back then was not so powerful. Now, he hasn't even grasped the 'form' of the Foundation of Existence and has only relied on cultivation to reach this realm. Why is he so powerful? What mistake did I make?"</p>

Dao Integration Tribulation, Mahayana, Origin of the Dao of Immortals of Ancient Times (5)