MTL - Dumb Please Take a Seat - Chapter 402 I'm pretty sure it's Gu Zhi

Bai Aoxue, the best mercenary in the 21st century, is accidentally sent back to the Chengxi Dynasty in Great Continent due to an explosion in her mission, and trapped in the first daughter of Prime Minister. After her rebirth, she is set up by her father to marry the 5th prince Jun Yeyan who wears a mask all day long.
In the face of bloodthirsty enemies, discord between brothers, collusion among courtiers and invasion of enemy state, can Bai and Jun resolve the crises? What will happen to their political marriage? How will the fierce battle for the throne end?
With many twists and turns, the book brings you to experience palace revolution, love and hatred thousands of years ago.

- Description from Novelupdates

Kaidan (Kaidan refers to eerie tales of strange, mysterious, rare, or bewitching ghosts and monsters from Japanese folklore.) feed on cognition, wield information as weapons, and use information as currency, existing between the peculiarities of neither life nor death.They exist in human rumors and dwell in the shadows of the world.“Does this mean I will become a Kaidan?”In ancient times, they were worshipped as deities, empowered by faith.“Then I am a deity!”In more recent ancient times, they were regarded as demons and fed on fear.“I will become the master of Kaidan!”However, as the tides of time washed over, they gradually vanished, leaving behind only texts considered to be delusions.“To restore the glory of Kaidan is an undeniable duty of ours.”But you are not yet a Kaidan, hmm, nor a person.“Well, becoming a Kaidan counts as success.”

Damon’s lips twisted into something between a smirk and a sneer. “Sisters or not, I kept them alive so you could watch me rip off their heads one by one. That’s the only reason they’re still breathing.”My jaw tightened. “You wouldn’t.”He leaned closer, his voice lower. “Wouldn’t I?”“You kept them alive?” I repeated his words slowly, my voice cracking with disbelief. “Just so I can watch you kill them?”Damon stood tall, his eyes twirled with something sinister, his expression was like a carved stone. “Yes,” he said flatly. “You cared enough to protect them. Now you’ll watch as I end them.”My chest tightened. The air grew too thick to breathe. “You’re cruel.”“I’m Alpha,” he replied, his tone cold, without a shred of mercy. “Mercy gets people killed.”‘Psychotic bastard. I wish I could drive a knife into your chest right now!’~~~~~~~~~~~~~~~~~~~~~~~~~~When Ember opened her eyes, she was no longer the powerful, independent woman she once was.Instead, she woke up in the fragile, abused body of a lowly Omega—destined to be nothing but a breeder for the Alphas.Her escape attempt didn’t get her far. Instead, it led her straight into the path of Damon Blackthorn—the ruthless Lycan King feared by all.Sold like a slave by her own father, Ember becomes the property of a man with a frozen heart and a violent temper. But beneath her submissive mask lies something more: a cunning mind and a will that refuses to break.Now, in a world ruled by dominance, power, and ancient bloodlines, Ember must do more than just survive.She must outsmart a king.She must earn the loyalty of the very people who scorn her.And maybe—just maybe—she’ll bring the Alpha to his knees.

The first great emperor in the world was betrayed by his confidante and perished. Millions of years later, the great emperor’s soul returned and was reborn as Ye Yan, the son-in-law who was kicked out by the Chu family with a letter of divorce, restarting the supreme journey. Open the gate of immortality, kill the Jiuzhongtian, and cast an invincible name again!

- Description from novelbuddy