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

As the name suggested, the Heavenly Rules were rules set by the Heaven Realm.

This was a rule that had existed since the birth of the Heaven Realm. It was an iron law that could not be changed. All living beings had to follow it.

Even in an era where the Heaven Realm disappeared and the Heaven Gate was closed, the Heavenly Rules still existed.

Without opening the Door of Heaven, one could not break through the Heaven Gate. This was the rule set by the heavens. No one could violate it, no one was an exception.

This was also the reason why after the Heaven Realm disappeared, many ancient experts either slept, faked their deaths, or sealed themselves.

That was because if one could not break through the Heaven Gate, they could only waste their lifespan and wait for death.

Only when the Door of Heaven reopened would they be able to break through the Heaven Gate and extend their lifespan.

One Step, One Gate, Flicking Through the Heavenly Ladder