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

Zhu Changsheng's eyes widened when he saw the key. His entire body trembled as he said excitedly, "So it hasn't been lost. It has always been here, hahaha!!"

He threw his head back and laughed. As he laughed, two streams of tears flowed down his face.

It was as if someone who had lost all his fortune and lived a hard life for many years had suddenly found all his assets again.

This joy and mood were really difficult to describe with words.

Cui Heng looked at Zhu Changsheng from the side. After the latter finished venting his emotions, he smiled and continued to ask, "Looks like Sect Master Zhu knows this key."

"Yes, yes, of course I know it. Our Plague Imperial Palace has been looking for it for 120,000 years." Zhu Changsheng stared at the key and said with a trembling voice, "This is the fundamental inheritance of the Plague Imperial Palace.

This Should Be Cautious Enough