Blood Demon Sect was one of the five greatest sects in Southern Domain. After they emerged victorious in the war against the four allied powers - Black Sieve Sect, Golden Frost Sect, Solitary Sword Sect and the Li Clan (Southern Domain) - they became the number one sect in the entire Southern Domain. One month after the war, they completely exterminated Black Sieve Sect and the Li Clan. The Solitary Sword Sect and Golden Frost Sect became their auxiliary branches.
After Meng Hao became the Blood Prince of the Blood Demon Sect, many unsatisfied figures decided to test him. Needless to say, the matter was settled after Meng Hao subjugated all of the sect's spirit severing patriarchs with a show of overwhelming and domineering strength.
During the Ancient Dao Lakes Erruption, many of the Blood Demon Sect's spirit severing patriarchs and Meng Hao got caught in the spacial rifts. Due to losing the bulk of their forces, the remaining patriarchs bore with the bullying of the other major sects. The Violet Fate Sect gave the Blood Demon Sect one of their dao lakes when Meng Hao was stuck in the spacial rifts, which earned them the goodwill of the Blood Demon Sect patriarchs, alike.. After returning, Meng Hao thanked them and didn't take any of their dao lakes to return the favor.
During the Southern Domain Civil War, tens of thousands of Blood Demon Sect disciples perished and even Patriarch Fifth Peak, one of their spirit severing patriarchs perished. Due to Meng Hao's overuse of his Eternal Stratum, the Blood Demon Grand Magic and his unbending will, tens of thousands of Blood Demon Sect disciples were saved from the same fate. After over a week of fighting, all seemed lost until Blood Demon arrived. After Blood Demon emerged, he killed the peak-dao seeking patriarch of the Solitary Sword Sect and made the peak-dao seeking patriarch of the Golden Frost Sect and the peak-dao seeking patriarch of the Li Clan Dao protectors to Meng Hao by wiping out their will, essentially making them a puppet.