The Backbender (Avatar: The Last Airbender) - Chapter 8 - : Revenge...

The Laughing Demon, Zǔ Zhòu, who had plunged the Nine Heavens into despair, met his demise by defying the Laws of the Dao. However, fate intervened. Transmigrated into a new body millions of years later, with his forbidden bloodline still bound to his soul, he seeks to live this new life as he did before, stopping at nothing, even if it means destroying the Heavenly Dao itself!

He Lang died by his own hands for the sake of his imperial younger brother’s ambition, whom he loved. He was offered to be reborn in exchange for giving up his past romantic feelings. Reborn without the burden of his romantic feelings, he brings with him a manual to new worlds. He wholeheartedly followed the instructions of the manual to complete the tasks, not knowing that the originally slag gong was blackening…
He pleaded to his affectionate Emperor brother to release him, he pleaded to the paranoid prisoner next door, but until the end he remained baffled.
In the end, he discovered that the full name of the manual was – “Slag Shou Cultivating Manual”
Σ (っ ° ° °;) っ!

- Description from Novelupdates

When Lu Wu opened his eyes, he found that the world had changed completely.The world before him did not have fancy magic, nor ultimate Dou Qi.What it had were summoners that form contracts with summoned beasts.And coincidentally, he was such a summoner, although not a professional one, and his first summoned beast was a piece of crap.But that was fine, because he also had a golden finger!

Three years ago, the animals and plants on Earth underwent crazy and unexplainable changes that included transformations, reversions, and the addition of otherworldly species. And it was the start of a brand-new type of profession in the new generation of humanity – Monster Trainers, people who specialized in taming monsters.