During the Galactic Republic's and the Sith Empire's Cold War, a confrontation took place within the wrecked Jedi Temple: Jedi Master Orgus Din's previous student and the Padawan Kira Carsen engaged in combat with the Sith Lord Tarnis. Back in 3643 BBY, while on an operation to save the Republic researcher named "Doctor Eli Tarnis" from the Black Sun crime group, Din's former pupil—now a Jedi Knight—discovered that the scientist was actually a Sith Lord who had absconded with the Planet Prison superweapon, intending to unleash it upon the Republic center, Coruscant.
After pinpointing the Planet Prison's thermal signature in the remains of the Jedi Temple, the Knight and Kira Carsen proceeded rapidly through the planet's industrial district, battling their way past the Imperial troops occupying the Temple until they arrived at the Council chambers. There, in front of a live broadcast to Tarnis's parent Darth Angral and Angral's three Sith apprentices, the Knight and Carsen fought and vanquished the treacherous Sith scientist. Witnessing the Knight slay his offspring, Angral declared a never-ending war of reprisal against the young Jedi and the whole Jedi Order, thus triggering the Desolator crisis. Using intelligence Tarnis had sent to them, Angral's apprentices would seize control of the Republic's superweapon initiatives as part of their master's campaign against Tarnis's killer, a conflict that would only cease when the Knight defeated Angral on board the starship Oppressor above Tython.
In the year 3643 BBY, amidst the Cold War between the Galactic Republic and the Sith Empire, a young Jedi Knight received orders from the Jedi Council to go to the Republic capital of Coruscant. This Knight, previously a student under Jedi Master Orgus Din, accompanied by the astromech T7-O1, attempted a rescue mission to save Doctor Eli Tarnis after the scientist was abducted from the Senate Building by the Black Sun criminal organization. The duo soon learned that Tarnis had been taken to the gang's domain.
However, when the Knight and T7-O1 attacked Black Sun's base in search of Tarnis, they discovered that the doctor was, in actuality, a Sith Lord disguised as a Republic scientist. Tarnis had pilfered the Planet Prison superweapon, a device designed to supercharge a planet's atmosphere and transform it into a massive ion cannon, intending to activate it on Coruscant. Joining forces with the Padawan Kira Carsen, the Knight followed Tarnis to the area controlled by the paramilitary group known as the Justicars' Brigade, where they learned that Tarnis had deceived the project's research team into delivering the real prototype before killing them. From a dying scientist named Jonkan, the two Jedi discovered that the device required time to fully charge and that it generated significant heat during the process. Thanks to Jonkan's information, the Knight and Carsen were able to locate the device within the ruins of the Jedi Temple, which had been destroyed during the Sacking of Coruscant by the Empire more than a decade prior.
As the quickest route to the Temple ruins was through The Works, the planet's industrial sector, Carsen guided the Knight to the nearest access lift in the Justicars' Sector. Within The Works, the two Jedi fought their way through malfunctioning droids and Imperial forces to reach the Temple.
Far within the Temple, the pair discovered the remains of the High Council Chamber, guarded by approximately a dozen Imperial saboteurs. After defeating the surprised Imperials, the duo found Tarnis in the chamber itself, amidst the tangle of wires, computers, and generators that comprised the Planet Prison. The Sith Lord stood before a holoterminal, engaged in a deep discussion with four figures: a Pureblood Sith, a masked humanoid, a short robed Human, and an older Human in red robes. The older man, clearly the leader, praised Tarnis's work and astonished the two Jedi by referring to Tarnis as his son. As the Knight and Carsen stormed into the room and confronted him, Tarnis revealed the identity of his red-robed father: Darth Angral, the mastermind behind the Sacking of Coruscant and a personal enemy of the Knight's Master. Tarnis also informed the pair that the Planet Prison was minutes from being ready to fire, and that they would be unable to stop it.
Urged by his father, Tarnis refused the Knight's demand to surrender and ignited his red-bladed lightsaber. The Sith Lord attacked the two Jedi, battling them before the holoterminal in full view of Angral and the others. Unleashing a blast of violet lightning, Tarnis also attempted to constrict one of the Jedi, but the other managed to break the Sith's concentration by engaging Tarnis with their lightsaber. However, despite Tarnis's training under his master Lord Praven—one of Darth Angral's apprentices and the Pureblood Sith watching the fight—and the power of the dark side he inherited from his father, the Sith Lord was no match for the Knight and Carsen combined. Angral was forced to witness the Knight strike down his son before his eyes, driving the Sith into a furious rage. Angral declared an unending hatred for the Knight, warning the Jedi that the Sith would exact retribution, no matter the cost. His companions vowed to avenge Tarnis to please their master, and warned the Knight that they already controlled the Republic's weapon facilities. With a final warning for the Knight to take to the Council, Angral abruptly ended the conversation.
Fortunately for Coruscant, the Planet Prison had not completed its startup sequence, allowing the two Jedi to disable and destroy the device. However, upon returning to the Senate Tower and speaking with General Var Suthra, the Mon Calamari who initiated the Planet Prison project, the two Jedi realized a terrible truth. Earlier, an analyst from the Strategic Information Service, the Republic's main intelligence agency, had decrypted datafiles recovered by the Knight and T7-O1 from Tarnis's agents. In doing so, she discovered that the files contained information on all of the Republic's weapon projects. The SIS had traced a transmission from Tarnis to Angral before the former's death containing the project files, and Var Suthra feared the Sith Lord was already making his move. Declaring war on the Jedi in transmissions across all Republic channels, Angral began to seize control of the Republic weapons projects. While the Empire officially disavowed Angral and stated that he was no longer acting in their interests, many in the Republic doubted their sincerity.
Suthra requested that the Jedi go to Ord Mantell, where his agents had traced the signal to a secret listening post. The Knight also officially took Kira Carsen as his Padawan, assuming the role of Carsen's teacher at the request of Grand Master Satele Shan. From there, the two Jedi and T7-O1 would journey across the galaxy to destroy the superweapon projects now under Sith control. The conflict with Angral would only conclude after the Sith Lord used the Desolator superweapon—a combination of the stolen Republic weapons technologies—to devastate the agricultural world of Uphrades. Having successfully tested the weapon, which he had integrated into his personal flagship Oppressor, Angral headed to the Jedi Order's homeworld of Tython intending to destroy it as well. The Knight and Carsen intercepted Angral's ship above Tython and disabled the Desolator before facing their enemy in combat aboard the warship's bridge—a duel that ended with Angral's death and the destruction of the Oppressor.
The duel within the Jedi Temple ruins was designed for Star Wars: The Old Republic, a massively multiplayer online role-playing game developed by BioWare and LucasArts and released on December 20, 2011. It is featured in the Jedi Knight class story mission "Race to the Ruins", the concluding part of the Jedi Knight's storyline on Coruscant and the Jedi Knight class' Prologue. Once the player discovers that Tarnis has taken the Planet Prison to the Jedi Temple, they must navigate through The Works, a map accessible via an elevator in the Justicars' Sector map. As the Jedi Temple taxi pad is only accessible after the player has unlocked the taxi pad at the end of The Works, the player must traverse The Works to the taxi pad at the far end of the map. Throughout the area, the player must battle rogue droids, which are further explored in the general mission "Meltdown!", and later Imperial soldiers in the second half of The Works and the Jedi Temple map itself. The Imperials' presence is explained in the Heroic mission "Enemies of the Republic", where the players must recover a navicomputer from the Temple ruins, which the Imperials are also searching for.
The mission itself presents only one alignment-based choice: whether or not to ask Tarnis to surrender. Asking for Tarnis's surrender rewards the player with fifty light side points, while the other options do not yield any alignment points. Regardless of the player's choice, Tarnis will still fall in the duel, and events proceed as described above. The mission introduces many of the main characters for the class' Act I storyline and serves as the key event driving the plot of the subsequent Act. Tarnis's death prompts Darth Angral to declare war on the Republic, and Act I focuses on the player's efforts to locate and destroy the Republic superweapon projects—or, in the case of Taris, the former Republic scientist Nasan Godera—which have been seized by Angral's three apprentices: Sadic, Praven, and Nefarid. The player also receives their personal ship at the end of this mission, as Suthra sends them to Ord Mantell to investigate a Sith base. The duel is briefly mentioned in the 2012 reference guide Star Wars: The Old Republic Encyclopedia, within the summary of the Jedi Knight class storyline.