The Principle of a Philosopher by Eternal Fool 'Asley' - Chapter 11.1, The Holy Warriors’ Vow

My whole life, all I wanted was power.

I churned the world into rivers of blood and eventually gained the title, “Demon Lord of Strength”. However, all this became useless when I lost to a party of heroes.

But what can a loser say? As I laid dying, I was forced to listen to the hero’s gibberish:

“If you are born again, I hope that you will live a kind life!”

But huh? When I opened my eyes again, I was back in the past.

“What do I have to do to live a kind life?”

This is the beginning of an ex-Demon Lord’s journey to live a kind

In the aftermath of a tragic incident, the soul of Zhang Fei was transmigrated into a sacred body in a world of cultivation. Joined by the consciousness of an ancient cultivator, Zhang Fei must find a way to survive in this deadly world of beast demons and immortal cultivators.

Traversing into another world, Zhang Xuan finds himself becoming an honorable teacher.

Along with his transcension, a mysterious library appears in his mind.

As long as it is something he has seen, regardless of whether it is a human or an object, a book on its weaknesses will be automatically compiled in the library.

Thus, he becomes formidable.

“Emperor Zhuoyang, why do you detest wearing your underwear so much? As an emperor, can’t you pay a little more attention to your image?”

“Fairy Linglong, you can always look for me if you find yourself unable to sleep at night. I am skilled in lullabies!”

“And you, Demon Lord Qiankun! Can you cut down on the garlic? Are you trying to kill me with that stench?”

This is an incredible story about teachers and students, grooming and guiding the greatest experts in the world!

- Description from Novelupdates