Forerunner

From ILB

Forerunner (plural appears optional) are an ancient race that appears to be the central point of the Covenant religion. They existed an untold number of years ago but none seem to remain. They are only apparent now by the artifacts they have left behind, including Halo, the monitor 343 Guilty Spark and a crystal buried on Reach known as the Holy Light. It is rumored that mankind and Earth may be tied to the Forerunner by some unknown connection.

More on the Forerunner via Halo Library (http://library.psyjnir.net/?id=5) and The Halo Story Page (http://halosm.bungie.org/story/forerunner.html).