Villain: I Must NTR All The Hidden Bosses! - Chapter 21: Initializing Clue System...

Name: ParadoxSpecies: Snake, ?Description: A tiny snake with great potential.That was who I was. That was what I was. A tiny snake with great potential. The sole creation of the Great Core.It was just us, the Great Core and I, tucked away in our little corner of the World Dungeon. Together, we hid from the bad-things and the Coreless of the world outside - safe from the horrors that would consume us.Until, one day, the Coreless found us. Until they tried to steal away my creator. Until, with no other option, I swallowed the Great Core that had made me.Only after that did I become what I was always meant to be.At last, I became the Great Core's Paradox in more than name.[The Endless Cycle] began.Thus begins the story of a little snake zealot and his journey to greatness.

This story is centered around the man named Yi Ji-Hyuk, who has spent 1000 years in a Medieval Western fantasy-like world before returning back to the modern-day Earth. When he returns, he finds that his home is facing monster threats, and that humans with superpowers have appeared to protect the innocent people of Earth.

A good-for-nothing man married a beautiful girl but was kicked off the bed on the wedding night. Furiously, he wrote a bill of divorce and ran away.
He was schemed a car accident in which he nearly lost his life. However, it turned out to be a blessing. He swallowed the soul that passed through the outer world, thus obtained superb medical skills and martial arts.
Later on, with the silver needles and invincible martial arts, he embarked on the road of counterattacks and was committed to his great dreams.

- Description from Novelupdates

Found a suitable body named Bai Xiao. Reincarnating into the World of Elementalists.

“Mission: Overpopulation of carnivorous fish in the lagoon.

Please kill 666 carnivorous fish in order to prevent the destruction of the lagoon’s ecosystem.

Reward: 20 Balance Points.”

“Mission: Forest fire.

Extinguish the fire.

Reward: 200 Balance Points.”

- Description from Novelupdates