Once the top cultivator in Tong Xuan Realm history, the Great Demon God was widely respected by all 3 Races of the world as a legend. Despite Tong Xuan Realm’s limitations, he managed to become a 1st Order Saint King. He would then prove a major hero for Tong Xuan Realm in defeating the invading Bone Race after gathering the powerhouses of all 3 Races to assist him. It is his legacy that was left behind to Yang Kai in the Black Book.
Personality
From what is seen, the Great Demon God seemed to have a rightfully confident personality as well as a knowledge of his limits and when to test them. He proved his heroic qualities by sacrificing himself for the good of Tong Xuan Realm.
Appearance
The Great Demon God’s statue and numerous memories depict him as an awe inspiring and proud figure with the Demon Eye of Annihilation overlooking everything with a sense of superiority.
Background
Known as the most powerful cultivator in Tong Xuan Realm’s history, the Great Demon God ruled with the Ancient Demon Clan as his most trusted servants. He was unique among the Demon Race in that he was an extremely accomplished Alchemist in addition to being the world's supreme cultivator. It was his legacy that Yang Kai inherited in the Demon Mystic Tome.
Origin
Later, it is discovered that Tong Xuan Realm’s Great Demon God was an independent clone that formed from the Demon Eye of Annihilation that once belonged to Mo Sheng in the Antiquity.[3] Yang Kai would later muse how his heroic actions contrasted greatly with the evil Mo Sheng.
Past
Long ago, the Great Demon God rose to prominence in Tong Xuan Realm. Under him, the Demon Race was the most powerful force in the world, and ruled over the Human Race and Monster Race. The Great Demon God was highly admired by the Demon Race to the point of worship. At some point he fought against one of the past Holy Masters of Nine Heavens Holy Land and defeated him.
Upon reaching the cultivation level of Saint King, the Great Demon God traveled to the Starry Sky to explore the higher mysteries of Martial Dao. However, after traveling in the Chaotic Abyss for awhile, he stumbled upon a giant Starship that made its way towards Tong Xuan Realm. On that Starship was the Bone Race.
The Great Demon God returned to Tong Xuan Realm and lead the three races in battle against the Bone Race. The Bone Race was defeated, but the Great Demon God was severely injured in the process of victory, and many of the leaders of the other races fell in the war. Before dying, the Great Demon God spent decades creating a giant Spirit Array, using the power of the Cultivation Star's Void Corridors, in order to hide Tong Xuan Realm away from any future invaders.[4] After leaving a Soul Clone behind to protect the Array, the Great Demon God sealed away the Ancient Demon Clan before dying.
Somehow, the Black Book carrying his entire legacy ended up in a Small World. Here, it would eventually approve of Yang Kai receiving the Great Demon God's legacy, allowing him to start his road on Martial Dao.