The event known to historians from the reformed Sith Empire as the Ritual of Nathema occurred in 4999 BBY. During this event, the Sith Lord Vitiate conducted a dark ritual that drained the Force from the entire planet of Nathema. While historians within the Empire viewed this as a great achievement for the Old Sith Empire, the Ritual was in reality the product of Vitiate's mental control over more than eight thousand Sith Lords. Vitiate, using his immense power, forced them to obey his will and siphoned their power as part of the ritual, which devastated the planet and made him immortal.
The Galactic Republic destroyed the Sith Empire in 5000 BBY during the Great Hyperspace War, leading the people of the Empire to fear that the Republic and their Jedi protectors would seek to eradicate the entire Sith species. Taking advantage of this fear, Sith Lord Vitiate acted while Supreme Chancellor Pultimo was organizing a purge of the Empire's remnants. Vitiate delivered speeches throughout the Empire, describing how the Jedi would not cease until the Sith were annihilated. By amplifying the Empire's terror, Vitiate then offered them hope: he arrived on the planet Korriban and summoned all remaining Sith Lords to meet him on his world, Nathema. There, he pledged to lead them in a powerful ritual of Sith magic that would guarantee the Jedi Order's destruction. Simultaneously, Vitiate instructed his scientists and researchers to find a planet where the Empire could rebuild without fear of pursuit by the Jedi.
Shortly after returning to Nathema in 4999 BBY, Vitiate learned from the head researcher about the discovery of a hyperlane linking Korriban to the long-lost colony world of Dromund Kaas. Three days later, Vitiate announced the beginning of his ritual, which drew eight thousand Sith Lords, including the surviving members of the Empire's ruling Sith Council. As each Sith arrived at his palace, Vitiate used his vast power to dominate their minds, binding their wills to his and harnessing their strength. He then commenced the ritual itself, which lasted for ten days. To achieve his aims, Vitiate employed the central computer of Zildrog, an ancient superweapon from the artificial world of Iokath designed for transferring life energies. This ritual granted Vitiate immortality and immense power in the Force, but it came at the cost of devastating the entire world.
The only species to survive the cataclysm on Nathema were the voreclaw, semi-sentient insectoid bipeds living underground. The ritual destroyed the voreclaw hive mind, reducing their colonies to groups of mindless individuals driven by hunger, who eventually emerged onto the surface. Lacking any other food source, the creatures resorted to cannibalism, attacking and consuming each other until Vitiate captured the few survivors and stored them in carbonite beneath the Sanitarium. The Ritual left Nathema completely devoid of the Force, and the planet's physical environment was distorted. To those on its surface, color seemed to have drained from reality, and the planet's orange sun appeared dull brown through the atmosphere. The newly immortal Vitiate abandoned his former identity, assuming the title of Sith Emperor and blaming the Jedi for Nathema's destruction. He then gathered the younger generation of the Empire's people and began a twenty-year journey from Korriban to Dromund Kaas. After reestablishing the Empire on Dromund Kaas, the Emperor purged all navigation data related to Nathema to prevent anyone from uncovering the truth of its fate.
However, members of the Empire's ruling Dark Council eventually discovered the planet's existence and history over a millennium after the Ritual, leading to a conspiracy to depose the Emperor and prevent future atrocities. This conspiracy was ultimately crushed, and by the time of the Great Galactic War with the Republic three centuries later, Imperial historians celebrated the Ritual of Nathema as a great achievement. Unaware of the true events, these historians believed that the other Sith Lords had willingly sacrificed their strength for the Emperor. The Sith Lord Scourge, having visited Nathema and learned the truth of the Emperor's rise from the conspirator Darth Nyriss, dedicated himself to preventing the Emperor from replicating the ritual on a galactic scale during the Galactic War between the Republic and the Empire. He informed the Jedi High Council of the Ritual's history to prove his sincerity.
Meanwhile, Vitiate continued to use Nathema for his own purposes. Unknown to both the Sith and the Dark Council, he secretly built another empire, the Eternal Empire, on the Wild Space planet of Zakuul under the guise of Valkorion. Vitiate maintained a Sanitarium on Nathema, where powerful Force-users who opposed him were experimented upon, unable to use the Force to escape or resist. The Sanitarium was guarded by Nathema Zealots, a secretive group of powerful Force-sensitives who could endure the horrors of the void in the Force through intense daily rituals and meditation. Vitiate kept the holocron containing the essence of his father, Dramath, in the vault beneath the Sanitarium, while another vault under an ancient Sith temple housed Zildrog, which Vitiate had deactivated after the ritual. Vitiate lived for over thirteen centuries by transferring his essence between host bodies, but around 3630 BBY his spirit was finally destroyed by the combined efforts of the Commander of the Eternal Alliance and Valkorion's biological children, Arcann and Vaylin. His death profoundly affected Nathema, miraculously revitalizing the previously lifeless world within a short period. Force-users no longer felt the unsettling "wrongness" upon setting foot on the planet, the air became fresher, and the weather more dynamic. Most importantly, vibrant plant life from seeds in the soil took root and flourished, dramatically changing the planet's once-desolate landscape. Escaped experiments from the Sanitarium provided some semblance of animal life, while surviving Zealots began settling in the abandoned wilds. Despite Nathema's return to life, experts could not determine the precise environmental mechanism that caused such an abrupt change.
The Ritual of Nathema was first detailed in Drew Karpyshyn's 2011 novel The Old Republic: Revan, though it was not officially named until the release of the BioWare–LucasArts video game Star Wars: The Old Republic later that year. One of the in-game Datacrons, holocron-like devices that permanently boost player stats, can be found in the Gorinth Canyon region on the Empire's version of Balmorra. The corresponding Galactic History entry in the in-game Codex describes the Empire's version of the Ritual of Nathema. The Ritual is also mentioned in the Jedi Knight class mission "An Unthinkable Alliance" during the game, although Lord Scourge does not name the planet.
The Journal of Master Gnost-Dural, a reference book released alongside the game, features Jedi Master Gnost-Dural's investigations into the Emperor's history, though he could not determine exactly what happened on Nathema. The 2012 reference guide The Essential Reader's Companion mentioned the event in its summary of Karpyshyn's novel, and the Star Wars: The Old Republic Encyclopedia also included a mention of the Ritual. Nathema was later featured in the game's Knights of the Eternal Throne expansion, where the story of the Ritual was recounted by the Force spirit of Vitiate's father, Dramath. An update set after Vitiate's final death revisited the planet in "The Nathema Conspiracy" flashpoint, which added to the Ritual's backstory by revealing Zildrog's involvement and showed the void in the Force dissipating and the planet returning to life, indicating that the effects of the Ritual were not irreversible, but lasted only for as long as the Force Entity Vitiates existence continued..