The Mysteries were a series of ancient Sith rituals and acolyte initiations that were conducted on the Sith World of Upekzar at five sacred volcanic cave systems that together constituted the Circle of Visions. These rituals and their associated sites individually dealt with different focuses and disparate aspects of the dark side, but universally made use of the rhak-skuri, a subspecies of diplura whose members produced pheromones known to cause nightmare-like hallucinations among certain humanoid species.
The more noteworthy among the five Mysteries were the High Rites, conducted by the strongest Sith Force users at an elaborate cave system in the temperate region of Upekzar; the Cold Rites, where practitioners tempered emotions and hardened their hearts; and the Rites of Fire, where acolytes focused their anger and passions into greater control over the dark side.