The Ciratu Spheres were a group of six spherical objects which orbited the star Ciratu in the Ciratu system, which was a part of the Immerian Outback sector in the Expansion Region, far from any trade routes. Composed of rock and iron, each sphere was filled with twisting tunnels. It was rumored that some scouts who had ventured into the spheres discovered wondrous machinery, while others were mysteriously altered by processes they could not remember. Some scouts were said to have never returned at all. It was widely believed that the spheres were created by the ancient race known as the Celestials.