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

The existence of an Immortal Emperor would distort time.

This was reflected on the River of Time. The "river water" kept raising waves and attacking this Immortal Emperor "lighthouse".

Once the pillar of light that supported the "sun" above was destroyed, the outcome could be imagined.

In a sense, this cultivation method was the true "profound mystery of seizing the creation of the world and invading the sun and moon".

"On the spectrum of time, Immortal Emperors are extremely powerful. They can even attack from the past to the present!" Cui Heng observed the influence of Immortal Emperors on the past, present, and future and was rather shocked.

This also meant that even a Return to Void cultivator like him, if he did not cultivate time-type spells, could be attacked by Immortal Emperors from other space-time dimensions at any time.

Even if he would not be killed, the feeling of being passively beaten would definitely not feel good.

The Huge Pressure from an Immortal Emperor