I Became the First Prince: Legend of Sword's Song - Chapter 3.1: Prince of Mangani (3)

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates

Existence was divided into three realms. The Heavenly Realm. The Earthen Realm. The Infernal Realm. Below them, countless minor realms of all types existed, none able to match the might of any of the Three Fundamental realms. The Celestials led the Heavenly Realm, The Immortals led the Earthen Realm and Demons led the Infernal Realm while the Rulers controlled all the minor realms. Together, they formed The Myriad Unity and allowed peace to reign supreme. The mortals were allowed to cultivate and reach for the Heavens as a balance was installed between the Heaven and Earth, all according to the Heaven’s Will. And yet, among the billions of trillions of living beings within the Myriad Unity, one seemed unsatisfied. “They are lying to us.” This man went against all known truths and contradicted the very gods. “We are in a false world! Mere pawns used to study an outcome!” And so in search of freedom and truth, this man committed the ultimate taboo. He rebelled.

The main character is reborn as a character from a game he played in his previous life. This character falls into ruin along with the villainess, spending the last of their years together. A man named Kururi Helan.

Promise transmigrated to the TYPE-MOON world and became one of the students of Waver Velvet at the Clock Tower.But a dream must eventually come to an end.Upon waking from a night's sleep, he recalled his identity as a transmigrator and also discovered his golden finger.A Heroic Spirit Class Card.It can take Promise to different eras, and by leaving behind corresponding legends, he can ultimately ascend to the Throne of Heroes!He thus travelled to ancient Greek mythology and Norse mythology.Promise: “I heard after death, you can ascend to the Throne of Heroes. What are you waiting for, come on, kill me!”(PS: This book is not a traditional simulator story; its content mainly revolves around the Age of Gods, hence the Age of Gods is a long narrative!I didn't use TYPE-MOON in the title as it was already too large)