Douluo Dalu: The Legend of Heavenly Ruler - Chapter 9: Serene Sword Arts...

Hiding in the Cold Palace and eventually becoming a Boss of Sorts. Li Mu was transported to a fantastical world and became a measly eunuch of the State of Xia. Despite having initially thought that his life would be a miserable one, he had unexpectedly acquired a check-in system.

Whenever our ship encounters a tenth-level storm, my comrades-in-arms will not have the slightest worry, because they know that I still have me on board.

- Description from Uukanshu

Sa Bina was on her way to write her SAT when she suddenly finds herself in a strange world. She is sent to be the old emperor’s concubine, but on their wedding night, the emperor gets murdered by no one other than his own son and the heir! To survive, Bina makes a deal with beautiful but deadly Lucretius and her life in this dangerous kingdom begins.

One day, Luo Jian woke up from his sleep and found himself in a locked chamber where the door and window were all sealed. A note with a few lines written on it was tacked to the wall: “Escape from this room within an hour, otherwise, you will die.”

There is a sequel called Reincarnation Night (轮回之夜) that takes place in the same universe but has different main characters

- Description from Novelupdates