Transmigration: Flirted with My Childhood Sweetheart - Chapter 634 - 633: Prescribing the Right Remedy and Achieving the Opposite Effect

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.

A scientific genius named Thomas Harrier was transmigrated to an imperial prince body after a car accident that took his life. He found out that he is in a world similar to our own with a timeline akin to early twentieth century. The body that he is occupying was the imperial prince of a failing empire who suddenly rose to power after a successful assassination attempt of his father. Unaware that the attack is just the beginning of what is to come. He faces many challenges throughout. Will Thomas Harrier be able to live his second life in peace while running an empire and getting it back to its former glory? Or will he succumb into a conspiracy lurking within the country's borders?

Expect some:

Cold war era techs.

Super battleship with advanced electronics, propulsion, and fire control systems?
Helicopters?
Missiles?
Modern medicines and equipment?
AC-130?
A nuke?
Challenger or Abrams or Leopard?
F-4 Phantom or MIG-21?
Colored TV's.

Everything!!!

PS. Cover not mine, I just found it on google.

A data loving young man from Earth has an accident which transports him to a dark land filled with terrifying creatures and magical powers. Fortunately for him, he has a Biological Assistance Chip to ease his path. However, things in this bizarre and strange world are not always as they seem, and, though it is a tremendous asset, the chip doesn’t always work as expected. With all of the crazy creatures and magical mayhem around him, one can only wonder what the future holds for this young man…

- Description from novelupdates

Heaven Concealing Great Sage Xie Chuan was plotted against by his enemy. Trapped within the God Burial Valley, he found a supreme martial technique hidden in a tomb called Demon Refining Heaven Swallowing technique.

Millions of years after the betrayal, reincarnated in a direct disciple’s body belonging to a small sect named Cloud Mist Sect, Xie Chuan finally broke out and escaped from God Burial Valley.

“In my previous life, I had only concealed the heaven with my hands. This life, I want to refine demons and swallow the heaven!”

The heaven swallowing expert who walked out of God Burial Valley was just born!

- Description from Novelupdates