The Sanitarium stood as the solitary structure preserved on Nathema's surface for centuries following the Ritual of Nathema, which annihilated all life on the planet. The Sith Emperor Vitiate persisted in utilizing the Sanitarium for his own agendas in the centuries that followed, constructing a fortified vault to safeguard some of his most confidential secrets. He conducted experiments, training Force-sensitive individuals to endure the Force's void, giving rise to the Nathema Zealots, who became the Sanitarium's protectors, while the daily operations were managed by specifically trained Abyssin Keepers. Force-users who posed opposition to Vitiate were confined to the Sanitarium for experimentation, stripped of their ability to access the Force for resistance or escape. Ultimately, Vitiate dispatched his daughter, Vaylin, to the Sanitarium for mental conditioning, making her the sole inmate to ever emerge from the Sanitarium alive.
Years afterward, Vaylin ascended to her father's Eternal Throne and, upon discovering her mental conditioning, commanded Jarak, the scientist responsible, to devise a method to reverse it. Following a breakthrough by Jarak, he summoned Vaylin back to Nathema and subjected her to a ritual of his design. However, the outcome deviated from the intended course, causing Vaylin's power to spiral out of control, resulting in fatalities in its wake. She eventually mustered the resolve to sever her bonds and departed from Nathema's surface, subsequently using the Force to remotely initiate the Sanitarium's destruction.
Following the Ritual of Nathema's eradication of all life on the planet, leaving a void in the Force on Nathema, Vitiate identified one of his hidden vaults there, storing artifacts deemed too perilous even for his use. This included a holocron containing the essence of his father, Dramath, whom Vitiate continued to torment over the subsequent centuries. He also transported groups of Force-sensitives to the planet, compelling them to confront the Force void in an effort to forge an army of exceptionally powerful, yet utterly subservient, Force users. However, his endeavors yielded only partial success; the ultimate result was the Nathema Zealots, a group of Force users who managed to survive contact with the void through a daily regimen of rituals and meditation that focused their power, while simultaneously diminishing their free will.
The drawback of this process was the Zealots' dependence on the void for their survival, rendering them catatonic upon leaving the planet's surface. Nevertheless, Vitiate repurposed the Zealots as guards for the Sanitarium, constructed above the vault. Vitiate exploited the void left in the Force on Nathema to confine powerful Force-users who opposed him within 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's daily operations. The vault was guarded by native Voreclaws, while the halls were patrolled by mutated creatures from various worlds, genetically engineered to instill fear, terror, and obedience.
Around the time of the Treaty of Coruscant, Vaylin, the daughter of Vitiate's alter ego Valkorion, had demonstrated both immense Force strength and an inability to control it. Deeming her a danger to others and a threat to his plans, Valkorion dispatched Vaylin to the Sanitarium on Nathema to instill obedience. Anomid scientist Jarak was provided with a laboratory within the Sanitarium and granted complete authority over Vaylin. Jarak subjected Vaylin to numerous horrors during her stay in the Sanitarium, as she underwent physical and mental testing amidst constant fear, pain, and isolation. Eventually, Jarak exhausted conventional methods and subjected Vaylin to torture using machines of his own design.
Ultimately, Vaylin's mind was shattered, and she transformed into a cruel, vindictive individual prone to outbursts. She remained unaware of the true purpose of her stay in the Sanitarium – being conditioned to become powerless against anyone uttering the phrase "Kneel before the Dragon of Zakuul" in her presence. Vaylin's mother, Senya Tirall, once attempted to rescue her daughter from the Sanitarium, but was intercepted 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 her 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, with his Eternal Throne first assumed by Arcann, and subsequently by Vaylin. Following a confrontation aboard the Gravestone that revealed her conditioning, Vaylin contacted Jarak again, leveraging her newfound authority as the Eternal Empress to command him to discover a method to break her conditioning. Jarak returned to the Sanitarium, where Vaylin provided him with numerous test subjects. Eventually, Jarak informed Vaylin of a breakthrough, and Vaylin soon arrived on Nathema, where Jarak explained that the process to break her conditioning would be even more extreme, with no prior survivors. Unaware that the Alliance Commander had followed her to Nathema in an attempt to stop her, Vaylin consented to the process. However, shortly after its commencement, it proved highly unstable, resulting in her power erupting throughout the Sanitarium.
The Void corruption proved impossible to contain, spreading rapidly and fatally draining anyone it encountered. Even Valkorion, an incorporeal Force entity, was not immune to its effects. Jarak himself escaped, but was confronted by Lana Beniko and the Alliance Commander. Jarak led the two to the Emperor's Vault, where, before being killed by a vault guardian, he provided them with a helpful suggestion on how to restore the Vault's power, ultimately enabling their escape. While Beniko and the Alliance Commander were restoring power and investigating Dramath's holocron, Vaylin successfully broke her bonds and departed from the Sanitarium, unaware of their presence. Once in orbit, she employed her newfound power to trigger the Sanitarium's destruction through the Force. Beniko and the Commander barely managed to escape the Sanitarium just before the last structure on Nathema was destroyed.
Following the Sanitarium's destruction, Gault Rennow hoped to discover other similar structures that might contain vaults filled with priceless artifacts for sale on the black market. Gault attempted to contact a former exiled Sith contact who had once mentioned the existence of such structures after consuming too many Tarisian ales, but Gault discovered that she had mysteriously vanished a few days after sharing this information.