Known only as ‘The Imprisoned One‘, a Rakatan who’s birth dates back to the Infinite Empire during it’s reign across the galaxy thousands of years before the events of SWTOR.

Unfortunately, the Rakatan attempted to use nanotechnology and the force to become an immortal being. His lust for power lead to his own Empire imprisoning him within a ‘Rakan Mind Prison’, an ancient force-powered device that could bind his conscious within for all of eternity.

Thousands of years after the Rakatan Infinite Empire fell, his being trapped within the Mind Prison was long forgotten, that was until a Rodian trader named Lurze Kesh on Korriban came into its possession.
The Rodian would then hand the Mind Prison off to Revan, who warned him about it’s power and told him to deliver it to a Hutt on Tatooine.

Revan tampered with the Mind Prison, which in turn warped Revan within, face to face with The Imprisoned One. The Rakatan then played riddles on Revan, bargaining for his release.

Revan eventually won over the Rakatan, who in turn, agreed to free Revan from the Mind Prison and in exchange, gave Revan guidance on locating a piece of the Star Forge.

Hundreds of years later, during the Cold War…

During the waning years of the Cold War within SWTOR’s vanilla storyline. The player be it Republic or Imperial comes into contact with Czerka on Tatooine.

Here on the desert planet, Czerka has been mining below the surfance, and has uncovered the resting site of The Imprisoned One.

The Rakatan unleashed the remnants of the nanomachine technology that he had attempted to make himself immortal with thousands of years ago, and infected and overrun the Czerka operatives on planet, turning them into controlled drones of the The Imprisoned One.
While Czerka locked down the facility, the controlled Czerka drones would escape, beginning to infect both Republic and Imperial forces on the planet.

It would ultimately be up to the player character to investigate and not only take down the infected Czerka drones to the Rakatan, but find and bargain with The Imprisoned One himself.

Sources:
Knights of the Old Republic 1
Star Wars: The Old Republic – (Tatooine Main Planet Storyline)