I have an Apocalypse City - Chapter 515 - : Solo Kill

This novel is also known as Phoenix Cry Firmament

The previous owner of Mu Ru Yue’s body had been poisoned. Because of this, her meridians were blocked, hindering her cultivation, which eventually led to her being known as trash. After being beaten to death, Mu Ru Yue, who had originally been a successor to a medicinal aristocratic family in Hua Xia, reincarnated into her new body.

They want to seal my path?

I will train to reach the peak of the realms!

They give me a foolish prince as my husband?

I can make do with him.

It would be easier for me to deal with him, rather than with other candidates who would be thrown at me in the future. I shall strive to become powerful enough that nobody will be able to mock or kill me!

- Description from novelupdates

Yeho is a distant relative to a king in a small kingdom. Even though he is a distant relative, his house was very poor, and his mother was addicted to gambling. One day North Empire asked for Princess Sooyoung to be a concubine of an old Emperor because she was known for her beauty. But the king really loved his daughter so instead he ordered Yeho’s older sister to disguise as Princess Sooyoung and marry the old Emperor.

Yeho told his sister to run away with her lover, and his sister had to leave her younger brother alone with his mother. After she ran away, Yeho asked his mother to give the things back to the king that she got for trying to sell her daughter, but his mother already used the gifts to pay off her gambling debt. He was trying to give the gifts back to the king to take away his order, but now he can’t do that anymore. He tells his mother to run away, and he disguises as his sister to go to North Empire.

After he got there, he was trying to tell the Emperor the truth and take away his life, but the Emperor went out for few days to look around his empire. When the emperor came back, he wasn’t as old as he thought.