Raidorl Seiken Senki - Chapter 18: The Iron Lady is in heat.

He became Arthur. He lived his life as Arthur and claimed Excalibur.Now, he has returned with a purpose.Beneath the surface of the world lies a twisted world known as the veil—an dimension where monsters are born from corrupted human emotions and desire. The deeper you go, the more terrifying they become.Each Layer is sealed. Each hides a god-like being, waiting to rise to the surface.Now, Sylas bears the responsibility of keeping the gate between both worlds from breaking.[Keys are passed down through generations.No one knows where they came from, but those keys can open doors to another world — a world filled with deadly trials. If you complete the trial, you return with blessings from gods, mythical beasts, and ancient warriors. The amount of blessings you earn depends on how well you perform.But if you fail, the door shatters… and you are gone forever.If you survive, you are given a permanent rank — a rank that decides your place in society for the rest of your life.]

The servant looked at the grieving princess. “Your Highness, the Regent Prince sent your scholar fiancé to the Western Butcher’s daughter!” 

The princess gritted her teeth, speaking to her servant that it matters not as she has other suitors in line. Many days later, much to her dismay, the servant ran in a hurry. “Your Highness, the Regent Prince expressed his intention of becoming your suitor! All other men in line were sold to Gou Lan Red District!”

The princess was distressed. She said to her servant it matters not. She’ll soon be married to Prince Fuma. Then the uneventful came. The servant once more ran to her, almost tripping in the process. “Your Highness, Prince Fuma was imprisoned at home! Meanwhile, there’s a red sedan chair waiting at your residence for your marriage! It was led by the Regent Prince!

The princess was stunned. For a day such as this to come, it seemed impossible. This nothing but a sad story of a female boss crossing back in time to hold the thick thighs of the big boss. But while raising him, she was eaten in the process.

A young man with an extraordinary mind is off on an exciting adventure when he mysteriously wakes up in the body of a feeble slave-guy in a different, rich in quirks world.

The main character, a selfish jerk, would use extreme means to achieve his goals. However, he never allows his base instincts to overrule his sense of decency. He always pays back both good and bad deeds.

Will his (terrible/excellent) mentality help him make a fresh start? Will he get through misfortunes and hardships of the new world?

Among the demons, the supreme ones are called “Great Saints.”

A young man leaves his mountain village and travels around the world. By unceasing efforts, he finally becomes a legend of the age.

- Description from Novelupdates