This lore can be found on Belsavis.
Republic: This codex is obtained after completing the mission ‘Sleeping Rakata’.
Over twenty thousand years ago, the Rakata ruled an empire hundreds of worlds strong. They enslaved armies of lesser beings, but slavery and war were only incidental to the Rakata way of life. Their Infinite Empire was built on the promise that the Rakata could reshape existence to suit themselves–they would warp space, peer through time, create and destroy species at a whim. To humanoid minds, the Rakata of old were mad hedonists and philosophers without conscience. For all their arrogance and their eventual fall (and they did fall, in time, when their power mysteriously faded and their slaves revolted en masse), the Rakata were supreme at their peak. They effortlessly merged their strength in the Force with technological genius, creating nightmarish and brilliant devices. Their achievements may never be matched; perhaps this is for the best.