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

Cui Heng's eyes were completely pitch-black, without any other colors. They were filled with a sense of destruction, emptiness, and peace. It was a gaze that symbolizes death. Wherever his gaze landed, all matter, void, Great Dao, laws, and so on withered and decayed, walking towards death.

Four million light years ahead was a Star Sea with a diameter of more than 200,000 light years.

Cui Heng's gaze crossed the void and landed on the sky above the Star Sea, looking from an angle similar to an endless height.

In the blink of an eye, hundreds of millions of stars went from their prime to old age. Then, they began to quickly collapse and decay, walking towards their final death.

Even the space where the Star Sea was, it quickly decayed and turned into a dangerous place in the universe. No living being could appear here anymore.

Origin of Death, 480 Million False Selves (3)