Tatakau Shisho - Volume 7, Chapter 3: The Shadow is Creeping Near – Part 3

[ Warning: Mature content (R-18)]In a world where the strong is king and weak don't have any right to even raise their heads.Eric, a boy of humble origin, was beaten to half-death state and thrown into the Demon abyss.Luckily, he survived and even got a life-changing opportunity in the form of [Godly Devil System]However...“What? I'm a half devil and the most suitable path for me is of a Dual Cultivator?!”Join Eric as he rises from the bottom, breaks the societal norms, and create a place himself for the world.

A teenager named Evan Mason was reincarnated into the magical world of Harry Potter and goes to school at Hogwarts!
With only his knowledge of the future and great talent for magic, he takes the path towards the top of the magic world, only to realize that ever step he took, changed everything!

- Description from Novelupdates

The formless ancient world was infested with despicable demons. They hunted and feasted on mankind, keeping the human civilization constantly in a weak and suppressed state.

[WSA 2025] To confront the threat posed by monsters and demons, humanity summons a hero endowed with a mysterious system and an unrivaled capacity for evolution. He becomes the last bastion of hope for mankind. However, one of his mistakes gives rise to a calamity far worse than the Demon King.This calamity is conceived in a dungeon, abandoned as a fetus by its mother, and raised by the Demon King himself. Upon the Demon King's death, all the restraints he had placed upon the creature are shattered. Thus, the hero's nameless son begins to lay waste to everything. The greatest calamity the world has ever known is born.