Path of the Berserker - Chapter 23Book 4:

Once an imperial princess, now reborn among the lowest of s*aves of the nobility.

You are the ruler, I am a subject, you want loyalty, I’ll give you loyalty. You are the ruler, I am the subject, you want my sacrifice, I will sacrifice for you. This lifetime, we’ll only be ruler and subject…… cannot become the one who accompanies you to experience everything.

A deposed empress, a failure of a substitute. Charging into battle, he was the emperor, and she, his general. But within the intimacy of their military tent, he was her husband, and she, his wife.

But everything was star-crossed. For the one he loved the most, he would push her into hell again and again.

- Description from Novelupdates

Li Xuan traveled through the world of immortality and opened the apprentice system, and both apprentices and apprentices could be rewarded for upgrading.

【Ding! Accepting apprentice Qin Yue, reward you: Innate Divine Power]

【Ding! Accept the apprentice Zhao Tian, ​​reward you: call the wind and call the rain]

【Ding! Apprentice upgrade, reward you: space shuttle]

….

Li Xuan, who accepted a bunch of apprentices, evolved infinitely in seclusion.

Ten years later, the Devil Emperor invaded and wanted to sacrifice the whole world, but no one could stop it. The disciples watched the world fall into despair in pain.

At this time, Li Xuan appeared and slashed a sword against the Demon Emperor under the watchful eyes of the public.

Boom!

The sky fell apart, the invincible Demon Emperor fell on the spot, and the entire dark world was swept away by a sword.

The disciples were horrified. It turned out that the strongest person in the world was actually the master who had been in seclusion for ten years.

- Description from novelbuddy

Bad End Night is a novel by Hitoshizuku-P, based on a series of Vocaloid songs, the NighT Series. The plot revolves around eight actors trapped in a never-ending play, seeking a way to escape.