The Retired Hero is an Extra - Chapter 143 - : Boss Monster

Supernatural, adventurous, fantasy, reasoning, competitive, fantasy, xianxia, ​​martial arts, magic, history, city, science fiction, war, mythology… Infinite world, infinite wonderful original world Infinite + Advent complete “Ultimate Fear”, ” “Dream Evolution”, “Fantasy Comes to Reality”, quality assurance

- Description from novelbuddy

A 20-year-old genius medical student transmigrated to a book she read during an experiment and became a female supporting character named Mo Li.

Apollo Kaiser, a boy who bore the unlucky fate of being unable to grow strong, was condemned by his family.

Discarded by his mother and abused by others, Apollo gives in to his rage.

However, this action results in his death. Many would believe it to be the end, but Apollo's death was a required catalyst.

The Demon Monarch System finds its heir and attaches to his soul, bringing him to a new world where he starts his journey to supremacy.

This difficult journey rife with conflict, conquest, and brutality shall serve as Apollo's temperance.

Watch as the heir of the Demon Monarch rises above all, conquers Sin, subjugates unthinkable enemies, and even brings about the destruction of worlds!

The rise of the next Demon Monarch begins...

Previously one of the ten greatest Martial Emperor, Gu Feiyang somehow died near the mountains of Heaven Wave.

Fifteen years later, Gu Feiyang crossed through the cycle of rebirth. He was back! But this time, he was in the body of Li Yunxiao. Since then, Li Yunxiao started a treacherous journey. The world is in turmoil once more!

- Description from Novelupdates