The Retired Hero is an Extra - Chapter 105 - : Reluctantly Eager Reunion

This is the story of a man who had no choice but to become a villain.But not just any villain because even villains have standards.This is the journey of a man learning how to become one. And to help him, the MC has access to an unlimited number of villains in his System Space, pulled from across all realities from every known dimension: Murim, Cultivation, Supernatural, Urban, Martial Arts, Mecha, and beyond.So what is it that Razeal can learn?What can he teach? And why?How can someone with knowledge from nearly every kind of reality reshape the one he’s living in?Someone with the potential to access everything the multiverse has to offer?Tired of seeing the same ideas repeated?The same system copy-pasted with no soul?No real character building no personalities, no free will?Come read this.Who knows you might find something worthwhile.

The end of the world is coming, the world has undergone great changes, and everything has changed. Plants, animals, and even insects, as long as there are living things, have mutated.
Become more powerful, and even evolved supernatural abilities, such as chickens and ducks that can fly to the sky, such as cats and dogs that can breathe fire.
But only humans, without any obvious changes, seem to have fallen from the top of the food chain to the bottom of the food chain overnight.
Any creature that can open its mouth to eat can treat humans as food.
But fortunately, this world has not completely killed humans. Gradually, humans discovered that they had the ability to cultivate compatibility with other creatures.
As long as it has a high degree of compatibility with some powerful mutant creatures, it can be used for its own use to achieve the purpose of protecting itself.
Fang He is a person who is very compatible with mutant animals, but it is also because of his ability that he has changed from the strongest to the stupidest.
Fang He, who was reborn, said, “Hmph, this time…”

- Description from novelbuddy

Jian Chen, the publicly recognized number one expert of the Jianghu. His skill with the sword went beyond perfection and was undefeatable in battle, After a battle with the exceptional expert Dugu Qiubai who had gone missing over a hundred years ago, Jian Chen succumbed to his injuries and died.

After death, Jian Chen’s spirit was transmigrated into a completely foreign world. Following an extremely fast growth, his enemies piled up one after another before becoming gravely injured once more.

On the gates of death, his spirit had mutated, and from that moment henceforth, he would tread on a completely different path of the art of the sword to become the sword god of his generation.

- Description from novelupdates