The Simple Life of Killing Demons - Chapter 45Book 12:

A genius schemer, creating an emperor!

“Only when your brother is happy can you be happy.”

She committed all kinds of evil deeds to make him Emperor. However, Artezia’s devotion was repaid with betrayal. It was the Grand Duke Cedric, a righteous enemy, that gave her a hand of salvation at the threshold of death.

“Devise a plan.”
“…”
“I can’t think of anyone but you who can reverse this situation. Marquess Rosan.”
“…”
“Lend me your strength.”

There is no plan that can reverse the already declining power and save the fallen empire. However, there is a method. To turn back time before everything went wrong.

With tears of blood she sacrificed her body to an ancient magic. This time, she will not fall.

Artezia, who returned to the age of 18 before death, resolved to become a villainess for the Grand Duke Cedric.

“Please give me your hand in marriage. I’ll make you emperor.”

In exchange for kneeling to the devil, the devil shall dirty her hands for you.

The first prodigal of the Mu family has returned from rebirth, changing the very colors of heaven and earth, rewriting the entire world.Possessing divine treasures and magical weapons, she is all-powerful. With debts of vengeance to settle and debts of gratitude to repay! Whether to walk sideways or upright, the posture is a free choice!Reborn with a divine artifact, she possesses foresight, attracting good fortune and avoiding disaster, earning her the title of the greatest diviner!The greatest diviner, with the swirling changes of the world in her palm. However, upon encountering that person, she is unable to control her own heart.“You calculate the heavens and the earth, but have you ever calculated my feelings for you?” A smile blooms on that person's handsome face, as if a deity has descended.The Mu family's prodigal son, reborn and overturning chaos. Only when he stands at the pinnacle do people realize this isn't the prodigal son, but the breathtakingly beautiful young lady! Many young talents beat their chests in regret, having missed the best opportunity to win the lady's favor.Yet that person smirks arrogantly, indulging in a tender kiss on her forehead: “Thank you for being blind to her worth, otherwise, how could I have such a beauty in my embrace?”

Chen Sha came to a world of immortal martial arts and was ordered to take charge of the world’s first sect.

Before his death, the previous chief told him:

“If you don’t become the best in the world for one day, you are not allowed to go down the mountain for one day.”

So he closed himself in painstakingly, crossed the heaven gate in his body, and faced off against the ancient and modern powerhouses…

…

Many years later, Chen Sha recalled the day he went down the mountain,

From the moment he descended the mountain, he was number one in the world.

In the next ten epochs, any gods and demons have returned, immortals and Buddhas have lived in the world, ancient powers and ancient gods have appeared one after another.

No matter how the times change, he has always been No. 1 in the world and has never changed.

- Description from novelbuddy

This story is centered around the man named Yi Ji-Hyuk, who has spent 1000 years in a Medieval Western fantasy-like world before returning back to the modern-day Earth. When he returns, he finds that his home is facing monster threats, and that humans with superpowers have appeared to protect the innocent people of Earth.