Mysterium

The Mysterium was a Forerunner collection of artifacts located on the equatorial ring of Maethrillian. There was an entrance located beneath the Councilors’ chamber in the amphitheater. Thousands of items were gathered from the edges of Forerunner space, brought to Capital, and stored there. Some artifacts were simply art pieces, while others were scientific curiosities. Some Forerunners knew what the artifacts’ purposes were, while many did not. Among the artifacts stored there were Abaddon, a Precursor construct, and the Domain. Over a century after the Great Purification, the IsoDidact and a group of Forerunners journeyed to the Mysterium to repair the Domain, which had been destroyed in the firing of the Halo Array.

List of appearances

 * Halo: Fractures
 * Promises to Keep