Martial Arrogance Dragon Soul - Chapter 15 - Give Me a Reason

Ruins stretched across the landscape in the apocalypse after the nuclear war.

In a world far more dangerous than the one he once read about, Nero Ravenclaw is reborn as the heir to Rowena Ravenclaw’s legendary bloodline. Armed with knowledge of the books and a mind sharpened by experience, he quickly realizes that this isn’t the same Harry Potter universe.It’s darker, deeper, and filled with wizards far more powerful than he ever imagined.Determined to carve his own path, Nero seeks to reach the apex of the magical world. As he unearths the secrets of the founders, navigates political intrigue, and clashes with forces both known and unknown, he must forge his strength to survive.With new ranks of wizards, powerful bloodline abilities, ancient magic, and a reimagined magical system, this is the untold story of a Ravenclaw who refuses to be bound by destiny.The wizarding world is far greater than anyone imagined.And Nero intends to claim his place within it.Disclaimer : I don't own Harry Potter or its characters (except the original characters I create).

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.