Skill Forge: Broken Extra Character - Chapter 21 - : Hidden Quest 6

A human from Earth is thrust into the [Hunter x Hunter] world, becoming the Zoldyck family’s defiant, red-eyed prodigy. They call me a genius and the rightful heir, but I say that’s Killua’s burden to bear.Armed with crimson eyes, and a subtle yet powerful system, I’ll rewrite destiny, upend the world, and embrace the chaos with a wicked grin.

The King of Hell sentences you to death by midnight, but I can ensure that you live past morning.

The young man, Qin Lang, received the inheritance of a poison school by chance. He uses poison to kill people, uses poison to save people and he uses poison to chase beauties. With body of ancient extinct poison and a body of a martial artist, he walks around the city, and wanders around in the underworld.

- Description from Novelupdates

Every human on Earth was transformed into a summoned monster and was summoned to another world.

The Imperial Court of Tang Empire became dim and corrupt. The Emperor believed eunuchs. The officials vied with each other for authority. The Tang Empire was about to collapse. The flouring Confucianism, Buddhism and Taoism eyed it covetously. The three sects wanted to contend for the domination of the whole world. Which one would win in the end? Or would they coexist peacefully at last? Armies of different nations invaded the frontier on all sides. People and the whole world were in extreme misery. Who could save them?