Warning: Wikipedia contains spoilers.
A dark side artifact that was created by the Rakatan Empire 24,000 years before the original film trilogy took place. A giant automated shipyard, the Star Forge drew matter and energy from a nearby star, creating a basically endless supply of ships.
As an artifact of the dark side, the Star Forge corrupted those that use it, feeding its desire for death. The Star Forge was responsible for the corruption of Darth Revan and Darth Malak, who had been powerful and honorable Jedi Knightss up until they discovered the Star Forge after defeating the Mandalorians in the Mandalorian War.