The Planet Prison was a superweapon engineered by the Galactic Republic during the Cold War against the reconstituted Sith Empire. Doctor Nasan Godera conceived of it, but a team of scientists under Doctor Tarnis—secretly a Sith Lord and son of the infamous Darth Angral—weaponized it. The intended purpose of this device was to blockade a planet in a non-violent manner. As the prototype neared completion, Tarnis plotted to seize it, intending to deploy it against the Republic capital world, Coruscant, through a complicated scheme involving the Migrant Merchants' Guild and the Black Sun crime syndicates. His plans were foiled when a young Jedi Knight killed Tarnis amidst the ruins of the Jedi Temple, leading to the device's destruction before it could be activated. Later, Darth Angral incorporated its technology, along with other weapons, into the ship-based Desolator superweapon. This weapon was used by the Sith Lord to devastate the planet Uphrades, although the Jedi Knight ultimately triumphed over Angral on his warship above Tython just before Republic fighters obliterated the vessel.
The Planet Prison's design centered on overcharging a planet's upper atmosphere with what amounted to a massive ion pulse, effectively transforming the entire atmosphere into a colossal ion cannon. Any vessels attempting atmospheric entry or exit would be instantly incapacitated. The engines and systems of any ship caught in the ion field would fail, resulting in a crash. However, a significant weakness of the weapon was its substantial energy requirement and the considerable time needed to reach operational capacity, coupled with the generation of significant heat during the charging process.
The Planet Prison project originated with Mon Calamari General Var Suthra, who, after witnessing the destruction of the Sacking of Coruscant by the Sith Empire in 3653 BBY and observing the fall of the Jedi Temple, sought new defensive measures. Doctor Nasan Godera, a brilliant scientist, had previously resigned from the Galactic Republic's service in protest of the Treaty of Coruscant that concluded the Great Galactic War and ushered in a volatile Cold War between the Republic and the Sith. Suthra repurposed Godera's unfinished technological designs into weaponization projects, intending to honor the Jedi who had died during the attack by ensuring a swift victory in any future conflict.
Doctor Eli Tarnis eventually took charge of the various weapon projects, focusing primarily on the Planet Prison. Unbeknownst to most, Tarnis was the son of Darth Angral, the Sith commander who orchestrated the Sacking of Coruscant. As a Sith [Lord](/article/lord-legends] himself, Tarnis infiltrated the project to gather intelligence. He led a five-person design team for the Planet Prison, which included an individual named Jonkan.
As 3643 BBY approached, the project was nearing completion, and the scientists were preparing for field tests. At this time, Tarnis contracted the Black Sun criminal organization to steal the design schematics. Black Sun assigned a Rodian named Vistis Garn to execute the task. Garn presented the heist as his own initiative to his primary employers, the Migrant Merchants' Guild, a rival criminal enterprise. Garn and his team infiltrated a military warehouse and stole the files from the facility's computer network. They also absconded with a shipment of advanced weaponry and ammunition, but Garn was identified by the building's security system in the process. General Suthra and Jedi Masters Bela Kiwiiks and Orgus Din tasked Din's former apprentice, a Jedi Knight, with retrieving the stolen files. Kiwiik's Padawan Kira Carsen and SIS Agent Galen were assigned to assist the Knight.
The Knight and the astromech droid T7-O1 attacked the warehouse where Garn had taken refuge, successfully recovering the files and weapons. While the Knight was at the Old Galactic Market during this mission, Tarnis orchestrated his own "kidnapping" by Black Sun, directly under the observation of the SIS and the Coruscant Security Force within the Senate Tower. The Knight and T7-O1 intercepted the kidnappers at the nearby spaceport, eliminating the Black Sun operatives with the aid of Carsen and the Coruscant Security Force. After defeating the Black Sun leader, Zeer, the trio discovered that Tarnis had been transported to Black Sun territory.
Journeying to the region controlled by the gang, the Knight and T7-O1 uncovered Tarnis's true identity as a Sith Lord and pursued him to the Justicars' Sector in an attempt to locate the Planet Prison device. There, they discovered the bodies of the project scientists, who had been deceived into delivering the actual prototype to Tarnis. One of the scientists, Jonkan, managed to inform the Knight that the weapon required a significant charging period and generated substantial heat during that process. Utilizing this information, the Knight and Carsen located the Planet Prison within the ruins of the Jedi Temple and pursued Tarnis there. Standing before holograms of Tarnis's father and Angral's apprentices, the Knight fought and defeated Tarnis, destroying the Planet Prison device in the process.
The Planet Prison technology was later repurposed by Tarnis's father, Darth Angral, who combined it with several other stolen superweapons to create the Desolator. Angral installed this device on his personal flagship, the Oppressor, and used the Desolator to devastate the Republic agriworld of Uphrades. The ionization of the planet's atmosphere was completely effective, preventing any survivors from escaping. The crew of the Republic medical frigate Daybreaker intentionally allowed their ship to be disabled by the field to provide aid to the survivors.
Having successfully tested the weapon, Angral moved his ship to the Jedi Order's homeworld of Tython, intending to use it as part of his vengeance against the Knight for his son's death. Above Tython, Angral deployed micro-burst versions of the Planet Prison, temporarily ionizing the planet's atmosphere and disabling the Republic fighters deployed against the Oppressor.
However, the Desolator also inherited the Planet Prison's power limitations, requiring extended charging periods. This vulnerability allowed the Knight, T7-O1, and Carsen to board the Oppressor and disable the Desolator before it could fire again. With the destruction of the Oppressor by Republic fighters, the last remnants of the Planet Prison technology were finally eliminated.
The Planet Prison was conceived for Star Wars: The Old Republic, a video game launched by BioWare on December 20, 2011. It features prominently in the Jedi Knight class storyline on Coruscant and is the first of several superweapons that drive the plot of the Act I narrative. Regardless of the player's alignment choices, the Planet Prison is destroyed after Tarnis is defeated.