Arpious of the Planes - Chapter 7 Servant?

In the world of Aetheria, there is one name that is feared by all. Yet, he is known more for his title, the Demon General. Whether it’s Gods or Demons, no beings dare to oppose his authority. He ruled Aetheria with an iron hand. Cities are destroyed on his whim. Countries are razed at his displeasure.This is the tale of his rise to power.This is the tale of his rise to Godhood.This is the tale of the rise of the Demon General.

Ling Xiao was a powerful martial expert who fell in battle and was unexpectedly transmigrated into another world. He began life anew in the body of a boy with the same name, a fallen genius of the Ling Family whose cultivation had been crippled in a surprise attack, and son to a father who had also suspiciously been crippled under similar circumstances. Armed with knowledge from his previous life, Ling Xiao aim to restore his strength and establish his place at the top of this new world

- Description from Novelupdates

Ethan Carter was a failed fantasy author who died overworked and bitter. When he wakes up in the world of his own unfinished novel, he finds himself reborn as Darius Wycliffe, a weak and arrogant noble fated to be killed by the protagonist, Lucien Ashford, the Archmage’s Disciple.But Ethan refuses to die so easily. Armed with his knowledge of the world’s secrets and a unique ability to rewrite spells, he dives into the forbidden magic he once created but never fully explored. As he grows stronger, he uncovers terrifying truths about the world he thought he knew.To survive, Ethan must defy destiny, master the deadliest of magics, and challenge the very hero he once wrote to be unbeatable. But what happens when the lines between hero and villain start to blur?