The Sanitarium stood alone on the surface of Nathema for centuries after the Ritual of Nathema extinguished all life there. The Sith Emperor Vitiate continued its use over the subsequent ages, constructing a fortified vault to safeguard his most valuable secrets. He experimented with training Force-sensitive individuals to endure the Force void, creating the Nathema Zealots, who became the Sanitarium's protectors. Day-to-day operations were managed by specially trained Abyssin Keepers. Force-users who opposed Vitiate were imprisoned in the Sanitarium for experimentation, stripped of their ability to use the Force and thus unable to resist or flee. Eventually, Vitiate sent his daughter Vaylin there for mental conditioning; she was the sole prisoner to ever escape with her life.
Years later, Vaylin seized her father's Eternal Throne and, upon discovering her conditioning, commanded Jarak, the scientist responsible, to reverse it. After Jarak made a significant discovery, he summoned Vaylin back to Nathema and subjected her to a ritual of his design. However, the ritual spiraled out of control, and Vaylin's power surged uncontrollably, killing everyone nearby. Ultimately, she found the strength to break free and departed Nathema, subsequently using the Force to remotely obliterate the Sanitarium.
Following the Ritual of Nathema, which eradicated all life on the planet and created a void in the Force on Nathema, Vitiate established one of his hidden vaults there, storing artifacts deemed too dangerous even for him. This included a holocron containing the essence of his father, Dramath, whom Vitiate continued to torment for centuries. He also brought groups of Force-sensitives to the planet, compelling them to confront the Force void in an attempt to forge an army of incredibly potent yet completely obedient Force users. However, his efforts only achieved partial success; the result was the Nathema Zealots, a group of Force users who survived the void through daily rituals and meditation that focused their power while suppressing their free will.
A drawback of this process was the Zealots' dependence on the void for survival, rendering them catatonic if they left the planet. Nevertheless, Vitiate repurposed the Zealots as guards for the Sanitarium, constructed above the vault. Vitiate exploited the Force void on Nathema to imprison powerful Force-users who opposed him in the Sanitarium, where they were subjected to experimentation, unable to employ the Force to escape or resist. In addition to the Nathema Zealots, the Sanitarium housed specially trained Abyssin Keepers, who maintained order within the facility. The vault was protected by native Voreclaws, while the corridors were patrolled by genetically engineered creatures from other worlds, designed to inspire fear, terror, and obedience.
Around the time of the Treaty of Coruscant, Vaylin, the daughter of Vitiate's alter ego Valkorion, displayed both immense Force abilities and a lack of control over them. Deeming her a threat to others and his plans, Valkorion sent Vaylin to the Sanitarium on Nathema to instill obedience. Anomid scientist Jarak was provided with a laboratory within the Sanitarium and granted complete control over Vaylin. Jarak subjected Vaylin to numerous horrors during her confinement, subjecting her to constant physical and mental torment, fear, pain, and isolation. Eventually, Jarak exhausted conventional methods and resorted to torture using machines of his own creation.
Ultimately, Vaylin's mind was shattered, transforming her into a cruel, vengeful individual prone to outbursts. She remained unaware of the true purpose of her stay: to be conditioned to become powerless against anyone uttering the phrase "Kneel before the Dragon of Zakuul" in her presence. Vaylin's mother, Senya Tirall, attempted to rescue her from the Sanitarium but was thwarted by Valkorion before she could remove her from the planet. Vaylin spent years in the Sanitarium, during which her brother Thexan was the only one to visit and bring her gifts. Eventually, her other brother Arcann brought her back home to Zakuul, marking his sole visit to Nathema.
Years passed, and Valkorion was eventually killed, his Eternal Throne claimed first by Arcann and then by Vaylin. After a confrontation aboard the Gravestone revealed her conditioning, Vaylin contacted Jarak and, using her authority as the Eternal Empress, ordered him to find a way to break it. Jarak returned to the Sanitarium, where Vaylin provided him with numerous test subjects. Eventually, Jarak informed Vaylin of a breakthrough, and she traveled to Nathema, where Jarak explained that the process would be even more extreme, with no one else having survived it thus far. Unaware that the Alliance Commander had followed her to Nathema to stop her, Vaylin agreed to the procedure. However, soon after it began, it proved highly unstable, causing her power to erupt throughout the Sanitarium.
The Void corruption became uncontainable, spreading rapidly and killing anyone it touched. Even Valkorion, an incorporeal Force entity, was vulnerable. Jarak escaped but was confronted by Lana Beniko and the Alliance Commander. Jarak led them to the Emperor's Vault, where, before being killed by a vault guardian, he provided a crucial suggestion on restoring the Vault's power, enabling their eventual escape. While Beniko and the Alliance Commander restored the power and investigated Dramath's holocron, Vaylin successfully broke her bonds and left the Sanitarium, unaware of their presence. Once in orbit, she used her newfound power to destroy the Sanitarium through the Force. Beniko and the Commander barely escaped before the last structure on Nathema was annihilated.
Following the Sanitarium's destruction, Gault Rennow hoped to discover similar structures containing vaults filled with valuable artifacts for sale on the black market. Gault attempted to contact a former exiled Sith contact who once mentioned such structures after consuming too much Tarisian ale, but she mysteriously disappeared a few days after sharing this information.