The Cult is an organization formed of only Dark Spirit Masters. They take pleasure in many evil acts, be they murder, terrorism, torture, or etc. The Cult was formed before the events of SL2. During SL2, it was known as the Holy Ghost Church. The Spirit Ice Douluo, Huo Yuhao, led his generation of the Shrek Seven Monsters, along with many other powerhouses, to destroy the Holy Spirit Cult. The cult was wiped out and no more trouble arose from them.
They were assumed to be wiped out, but reappeared again in SL3. In SL3, they are a terrorist organization that mostly always remain in hiding, spread out across the three continents of Douluo, Star Luo, and Dou Ling. They kill in order to raise their cultivation by feeding on a person's negative emotions, blood, soul power, and etc.
With the help of the Federation and the Qiangu family from the Spirit Pagoda, they were able to smuggle two Godkiller-rank fixed soul ammunition inside Shrek City and detonate them, destroying Shrek Academy and Tang Sect. They lost many dark spirit masters and a total of seven Tittle Douluo. The Ghost Sovereign was gravely injured during the attack.
Later on, they allied themselves with the Abyssal Plane and opened a passage in the Extreme North causing a large scale world war to occur that lasted a few months. In the end, all the top level powers were killed in the war and the cult was once again destroyed into remnants.
Soul Land IV (Book 28)
While being the top powerhouse and a survivor of the Qiangu clan, Qiangu Qingfeng secretly returned to the Douluo Federation's Spirit Pagoda as a new "person" and gradually climbed its ranks. Later, Qingfeng worried about his lifespan eventually running out and out of fear of death, regathered and studied the Holy Spirit Cult texts, but wiped out the remnants. While keeping his morals and virtue, Qiangu Qingfeng self-completed his amateur path to improving himself and attaining longer life, as well as helping future Evil Spirit Masters adapt and start as Good path as members of society. The Holy Spirit Cult continued to exist in name, but reformed under Qingfeng into the Douluo Federation's top and virtuous hidden hero organization for humanity's development.