After Transmigrating as a Demon, I've Been Adopted by Angels! - Chapter 249 - Demons also Speak the Truth. Demons have Ulterior Motives!

The Third Miss of the Qin Clan is a useless and timid person. When the Prince withdraws from her marriage, she commits suicide by jumping into the river. In the 21st century, Qin Chu, a genius agent, is framed and his soul crosses over to the Third Miss of the Qin Clan. So what if she’s useless,

Qin Zhaoyue, a hundred-year-old Soul cultivator and famous artifact refiner, dies and transmigrates into a body of 16-year-old Xi Zhaoyue, who was killed on her wedding day.

The unlucky previous owner of the body was an illegitimate daughter of an influential family and was forced to live her whole life in the orphanage. However, at the age of 16, her Guide glands were awakened and as fate willed it, Xi Zhaoyue happened to have the highest compatibility with the youngest, bravest, most handsome Major General of the Empire, a dream husband of the whole Outer Space! Finally, a loving family she so longed for was within her reach… Yet, at the wedding ceremony, her Mental sea was invaded and she died.

Once Zhaoyue figured out the situation she landed herself in, she vowed: she wouldn’t be a proud and self-respecting cultivator, if she didn’t strive for independence, for the right to live the life freely! Cultivate, refine, get stronger! Become your own person!

- Description from Novelupdates

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates