The ancient Sith from Upekzar were known for performing their Mysteries' High Rites inside an intricate volcanic cave system. This was one of five such cave systems that together formed the Circle of Visions. Similar to the other locations along the Circle of Visions, the cave system used for High Rites was populated by a colony of rhak-skuri, a subspecies of diplura. These creatures emitted pheromones that induced nightmare-like hallucinations in certain humanoid species. Additionally, an old Sith city was situated three kilometers from the cave network.
The High Rites were conducted within a sprawling cave system comprised of lava tubes and caverns that were artificially constructed. These were located beneath a sleeping volcano in a temperate zone of Upekzar. The ancient Sith who initially colonized the Sith World of Upekzar considered the High Rites site to be of great importance. Over time, it was expanded to include several artificial caves where the Sith carried out their Mysteries' High Rites or prepared those who were to be initiated for their ritualistic journeys through the caves. In 44 ABY, Natua Wan, Ben Skywalker, and Vestara Khai explored one such cave, finding Sith lightsabers alongside remnants of decaying rugs and cushions. This cave also featured an inscription in Sith language on the wall, which stated: "Initiates, those who seek to master the dark side, prepare yourselves. Leave your weapons and your former selves in this chamber—or depart now and forever in shame, before it is too late to turn back."
This cave system, like the other four sacred systems along the Circle of Visions, was inhabited by a colony of rhak-skuri, also known as "dream singers" in the Sith tongue. This subspecies of diplura hunted using a specific pheromone that caused nightmare-like hallucinations in some humanoid species. The Sith who initially explored and settled Upekzar developed several dark side rituals that involved the use of the rhak-skuri pheromone, eventually transforming the caves into nexuses where the dark side thrived. By 44 ABY, the rhak-skuri within the High Rites cave network had evolved into two-meter-tall insects with some degree of sentience. They could recognize and communicate telepathically with Sith, and distinguish between light-sided and dark-sided Force users.
The caves where the Sith performed their Mysteries' High Rites were part of a group of five sacred volcanic cave systems. The ancient Sith of the old Sith Empire knew them as the Circle of Visions. Unlike the locations for the Rites of Fire and the Cold Rites, the High Rites caverns were visited only by the most powerful Sith Force users on the planet. Most of these Sith lived just three kilometers from the cave system, in a city nestled in the shadow of a dormant volcano. Inside the cave system, the Sith conducted the Mysteries' High Rites, which included various dark-sided rituals of Sith magic and initiations for Sith acolytes. These rituals involved the native inhabitants of the caves, the rhak-skuri. This insectoid species of diplura hunted using a pheromone that induced nightmares and hallucinations in humanoid species. Over the following millennia, the residual dark side effects of the Sith rituals caused the rhak-skuri to evolve into two-meter-tall predators that roamed the caves freely.
In 44 ABY, during the Jedi Order's search for Abeloth and Ship, Grand Master Luke Skywalker led a large Jedi strike team to the High Rites' cave system on Upekzar. While Skywalker and his Jedi searched the ruins of the ancient Sith city for signs of Ship, his son Ben Skywalker, former Sith Saber Vestara Khai, and Jedi Knight Natua Wan explored the caves and encountered a group of mutated rhak-skuri. The creatures attempted to feed on Skywalker, ignoring Khai's attempts to distract them because they recognized her as a Sith. To prevent Skywalker from being harmed, Khai sacrificed Wan to the rhak-skuri. As Abeloth triggered a trap that caused the volcano to awaken, the two surviving Force users were forced to quickly escape the caves.