From The Old Republic Wiki

The Rakata are an amphibian-humanoid species, who ruled an "Infinite Empire" of 500 worlds, several thousand years before the formation of the Republic. They completed the enormous structure known as the Starforge. During the travels of Revan (Knights of the Old Republic), it was discovered that this race went into decline due to the combination of a civil war and genetic plague. It is not known exactly when this happened, but around 3000 years after their discovery they became extinct.[1]