The Star Forge was a giant automated shipyard, designed to create the most powerful army of all time. It was constructed by the Rakatan Infinite Empire in 30,000 BBY, five thousand years before the rise of the Galactic Republic. The Star Forge drew energy and matter from a nearby star which, when combined with the power of the Force, was capable of creating an endless supply of ships, droids, and other war material. The Rakata, also known as «The Builders,» constructed the massive space station through the use of slaves from many subject worlds including Belsavis, Corellia, Coruscant, Dantooine, Drall, Duro, Kashyyyk, Manaan, Selonia, Sleheyron, Malastare, and Tatooine. This technological marvel came at a terrible cost, as the Rakata were by nature a cruel and savage species; the Star Forge began feeding off these negative traits inherent in its creators. As a result the Star Forge became an immense tool of dark side power.
The Star Forge, now a fusion of technology and dark side energies, began corrupting the Rakata in order to gain the immense power it required to operate itself and ultimately caused the collapse of the Rakata Empire. Aware of the semi-living superweapon’s ability to corrupt its users, Darth Revan limited his contact with the dark side artifact to avoid allowing it to control him as it did the Rakatans. His apprentice Darth Malak, on the other hand, planned to explore deeper into the Star Forge after disposing of his Master.
The Star Forge first appeared in the video game Star Wars: Knights of the Old Republic, published by BioWare in 2003. In development of the game, LucasArts gave BioWare feedback on the Star Forge’s design and said that it was a little too close to the Death Star.
In the non-canon dark-side ending of Knights of the Old Republic, the reborn Darth Revan and his apprentice Bastila trick the Republic into attacking the Star Forge in order to distract Malak; once they arrived, Bastila and Darth Revan fought throughout the station to the command center, where Revan faced Malak’s three most powerful Dark Jedi Masters (each with different robes). Malak promises that the one who delivers the killing blow to Revan will become his new apprentice. Revan and Bastila fought and killed all three of them.
Bastila remains in the command center in order to turn the tide of the battle in favor of the Sith fleet, while Darth Revan fights his way to the observation platform, where he confronts and brutally slays his former apprentice Malak and the Sith fleet destroys the Republic fleet.
Darth Revan returns to Lehon, where the celebrating Sith officially recognize him as the Dark Lord of the Sith. Revan then takes control of the Star Forge, and he’s poised to unleash the Sith fleet on the Core systems. However, Revan relocates back to Korriban, where he experiences an increasing number of visions of what he’d seen of the True Sith between the Mandalorian Wars and the Jedi Civil War. He then abandoned his conquest of the Republic and instead ventured into the Unknown Regions to face this threat, nominally leaving Bastila Shan in charge. Without a strong dark-side user to protect it, the Star Forge went dormant and stopped all production or activity.
There was also a deleted scene where the Star Forge was to fire a beam that could control gravity. This beam was to be shot at one of the Republic ships and drag it into a Hammerhead-class cruiser, destroying both. This was cut in the end.