The Dark Force represented a religious belief system centered around the dark side. This belief system originated at the Dark Force Temple, an ancient Sith temple situated on the planet Dromund Kaas. The core tenets of this religion were based on the teachings of Plaristes and Dak Ramis.
The Dark Force cult began its rise nearly one thousand years prior to the events of the Battle of Yavin. Back during this time, the most powerful Dark Lords of the Sith were Darth Cognus and her apprentice, the three-eyed mutant known as Darth Millennial. As adherents to the Banite Sith, they were bound by the Rule of Two, a principle dictating that only two Sith could exist simultaneously: a master and their apprentice. However, Millennial eventually found this doctrine to be overly constricting. Although disagreements with his master were common, Millennial ultimately defied Cognus' teachings one too many times. Barely escaping the confrontation with Cognus, Millennial sought refuge on Dromund Kaas, a planet steeped in Sith history. Within his new sanctuary, Millennial continued to contemplate the Sith teachings while also delving into the works of Plaristes and Dak Ramis, two controversial philosophers from over 25,000 years in the past.
Millennial started to believe that the Force itself had chosen him as a prophet. He then established a new religious group known as the Dark Force and proclaimed himself the Supreme Prophet of the Dark Side. His philosophy, which combined his Sith background with the writings of Plaristes and Ramis, started to attract numerous followers. While some of these new cult members were highly intelligent, many others were far more gullible. Regardless, anyone who questioned the principles of the Dark Force was sentenced to death for committing heresy. Even after Millennial's death, his cult continued to thrive. In the second century before the Battle of Yavin, a Jedi Padawan named Kibh Jeen was even swayed by the Dark Force's philosophy, although he was defeated in a space battle in 181 BBY. At some point, the fallen Jedi Kadann and his apprentice Jedgar made their way to Dromund Kaas, where they discovered the Dark Force Temple. They then decided to join the cult.
Sometime before the collapse of the Galactic Republic, Darth Sidious, the last of the Banite Sith, visited the Dark Force prophets. Sidious, intrigued by their distinctive understanding of the Force and their remarkable ability to foresee the future, resolved to enlist them into his service. He managed to convince Prophet Kadann that the future he was seeing was not his own, but that he was merely a messenger. By serving him and his carefully crafted plan to dominate the galaxy, the Prophets of the Dark Side would fulfill their true purpose. By swearing allegiance to Sidious, the clergy of the Dark Force were reintegrated into the Banite Sith lineage. Sidious then incorporated the Prophets as his advisors, and Kadann was appointed the Supreme Prophet of the Dark Side. Some years later, Sidious' plans came to fruition when he replaced the Galactic Republic with his First Galactic Empire.
With the establishment of his New Order, the Sith Lord, now the Galactic Emperor, designated the prophets as the Emperor's Mages, collectively forming the Secret Order of the Empire. Many of the Emperor's Dark Jedi, Jedi-hunting Inquisitors, Force-sensitive military officers, and Emperor's Hands were first introduced to the dark side through the study of the Dark Force religion on Dromund Kaas, under the guidance of the Prophets. While Kadann remained the Supreme Prophet, other important figures rose within the cult. Among them was Lord Cronal, a particularly cruel and twisted Human warlock who may have been fathered by a Dathomiri witch. The former Jedi archaeologist Jerec also studied the Dark Force religion, and he developed a strong connection with Cronal. Finally, Kadann's apprentice Jedgar was named High Prophet.
Even though Palpatine had appointed Kadann as Supreme Prophet, Kadann's true allegiance remained with the Dark Force. In the time leading up to the Battle of Endor, Kadann's visions indicated a likely restoration of balance to the Force. While Palpatine was not pleased with this prophecy, Kadann refused to change it. He was then forced to flee the Emperor's anger along with some of the Mages, while others stayed behind with the Emperor. Those who sided with the Emperor were led by Lord Cronal. As Kadann and his religious followers escaped to their Supreme Prophet's stronghold on Bosthirda, the Dark Temple on Dromund Kaas was left abandoned.