The Academy's Terminally Ill Side Character - Chapter 71: Introductory Monster Ecology [1]

After dying from betrayal, Thomas reincarnates as Jolthar Kaelzhar, the neglected son of a powerful clan, just after his brothers kill him. With Jolthar's memories and the blessing of Qalena, Thomas vows to rise from his lowly position and claim power in his new life.

Su Mo is a late bloomer, introverted and not very good at communicating with strangers.

I thought that my life would be so dull, but after participating in a national game “Star Ring”. Rediscovered the joy of life and embarked on the road to the top of the throne.

- Description from novelbuddy

Once upon a time, the Devil fell in love with one of the King’s many wives. One night he went to her room disguised as her husband and made love to her. She got pregnant with his child. Knowing this The King ordered her execution believing his wife cheated on him, but then the Devil appeared to the king making him a deal. In exchange for great power for his Kingdom, the King will let his wife Sire The Devil’s Child. The King who was greedy for power agrees to the deal and his Kingdom becomes one of the most powerful Kingdoms and the Devil’s Child, the seventh Prince of the Kingdom.