Kalatosh Zavros, a Togruta male, achieved the rank of Jedi Master within the Jedi Order. His service to the Order ended when he embraced the dark side, subsequently serving in the Sith Empire under the leadership of both Darth Revan and Darth Malak.
Kalatosh's journey began early in life with his acceptance into the Jedi Order. He progressed to become a Jedi Master, specializing as a Guardian of the Order through rigorous training. During the tumultuous period of the Mandalorian Wars, Kalatosh defied the Order's explicit directives by aligning himself with the Revanchists. As the Jedi Civil War erupted, Kalatosh succumbed to the allure of the dark side and pledged his allegiance to the Sith Empire. By then, he was known to wield a lightsaber that emitted a purple blade. In 3956 BBY, he met his death on Taris during its destruction orchestrated by Darth Malak. The planet's bombardment obliterated his physical form, transforming him into a Force ghost who lingered on Taris for centuries, leading up to the Galactic War.
In 3642 BBY, Kalatosh initiated a period of chaos on Taris, prompting responses from both the Jedi Order and the resurgent Sith Empire who dispatched individuals to address the situation. The Jedi sent Ashara Zavros, a descendant of Kalatosh from a lineage of Force users, while the Sith deployed a Sith Inquisitor, Lord Kallig, with the mission to control the dark ghost and corrupt Ashara.
Following Kallig's successful execution of the Force walk ritual on Kalatosh and the subsequent corruption of Ashara, he extended the ritual to Horak-mul. After binding both Kalatosh and Horak-mul, the Sith Lord aimed to use his newly acquired power to eliminate Darth Thanaton. However, the combined power of four Force ghosts proved overwhelming. As Kallig's physical body began to deteriorate, the ghosts threatened to shatter his sanity, compelling Kallig to devise a method to subdue them.
After using the Mother Machine on Belsavis to mend their physical form, Kallig traveled to Voss in an attempt to suppress the ghosts. Kalatosh, unfamiliar with Voss, questioned Kallig's sanity. Nevertheless, with the assistance of Hadrik, a Gormak Force-shaman, Kallig managed to use a mind-healing ritual to subdue the ghosts.
After Kallig triumphed over Thanaton and ascended to his seat on the Dark Council, the ghosts, with the exception of Horak-mul, implored to be released. Their requests were denied, and Kallig asserted his dominance over them.
The ultimate fate of Kalatosh Zavros is subject to the choices made by the Sith Inquisitor. He could be absorbed, set free, or redeemed alongside the other ghosts, potentially merging with the Force. Should the latter occur, he expresses an unfamiliar sensation, which Horak-Mul identifies as the feeling of freedom.