From A Stronghold NPC To The Final BOSS - Chapter 1043 - : Don’t contact me in the near future

A man who was once called the world’s strongest agent ended up becoming a teacher after his retirement, to train a new generation of agents. After many years of training his disciples, he was killed at the age of 60 by a secret organization’s ruse and was reincarnated in another world with his memories intact. Though he was surprised by the existence of magic and the strange species in that world, he quickly adapted to his condition as a newborn and took advantage of it. He acquired special magic and gained a massive amount of strength thanks to his rigorous discipline, in order to reach his goal: Resume his career as a teacher which he left halfway through in his previous life. This is the story of a man, who, based on the memories and the experiences of his previous life, became a teacher who travels through the world with his students.

How long will it take for a murdered thief to distill into something monstrous? In this story the darkness only grows stronger, and its reach only grows wider as it expands by devouring the life that surrounds it. This is a dark fantasy where evil is a where, not just a who that focuses on slow progression, undeath, and atmospheric storytelling.

Jang Joonbum started stream to enjoy an easy life.

This was a fragmented and disorganized world, this was a place that had been forgotten.

That day, was the most frustrating time for Ning Cheng, when on that day, he was abruptly brought here.

Because this world had Ning Cheng, who would imprint his name in the vast heavens, it would finally shine in the endless universe!

- Description from Novelupdates