The Author is an Extra, The MC is a Reincarnator - Chapter 19 Sparring [1]

Have you ever thought a monster that has a job of a summoner and a tamer

what should it call itself Monster Summoner? Monster Tamer? but he itself was a monster too

Watch as our mc travels the world as an reincarnated human who turn into a monster

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

Rinkai was an ordinary orphan with nothing but dreams of a brighter future. Honest and hardworking, he believed that effort would one day change his fate. But a tragic accident shattered everything.When he opened his eyes, he was no longer in the world he knew. Instead, he found himself in a realm where strength was absolute, and the weak had no place. Just as despair crept in, a mysterious voice echoed in his mind—[Ding! The Lucky spin System has been activated!]With a system that could grant him anything through sheer luck, Rinkai’s journey in this unpredictable world was about to begin.

A top hacker was chosen by the Lord God to be reborn into countless worlds, always as an expendable villain.

With no free will, every world became a dead end. Every one of his lives ended tragically.

Finally, after wresting control of the Villain System, this ace hacker decided to enact revenge. Even if his very bones were rotten, he’d choose to occupy the very heights of morality, if only on the surface.

Thus, he would change his fate as an abused slag.

- Description from novelupdates