Forerunner

From Halopedia, the Halo wiki

Summary

The "Forerunners" is the translated Covenant name for the race that built The Halos. It is theorized that this same race is responsible for the artifact that was found on Reach, and on Sigma Octanus VI.

The artifacts appear to have originated on different worlds, but have somehow made it onto these other planets. These artifacts are our only means of finding information about the Forerunner.