Generally referred to as the Dreadnought due to its formidable size and firepower, this immense Forerunner keyship supported the Librarian during the Conservation Measure, transporting species to the Ark for indexing and archival until after the Halo rings fired. Once the Flood was defeated, the dreadnought assisted in re-seeding the Milky Way using hidden slipspace portals placed throughout the galaxy.
However, long years after the Conservation Measure had drawn to a close, an enduring shard of Mendicant Bias would awaken on the Ark and access the ship, hoping to utilize it in an effort to reach humanity. Unfortunately, the ancilla’s journey would be cut short, and the vessel crashed onto the San’Shyuum homeworld of Janjur Qom - its impact creating an enormous sea which would come to be called the Great Apothtea. Many years later the San’Shyuum would regard the ship as a religious artifact, and eventually, a radical sect of San’Shyuum took it into space in an effort to find other Forerunner artifacts.
During their travels, the San’Shyuum encountered the Sangheili species on the world of Ulgethon, and after a series of devastating battles across a number of colony worlds, the Covenant was forged. The ancient Forerunner dreadnought, which still held Mendicant Bias’ dormant shard, was installed at the heart of the Holy City of High Charity. Though this effectively decommissioned the vessel as a weapon of war, it went on to provide power to the entire station and acted as a central point of worship for the Covenant. In 2552, the High Prophet of Truth abandoned High Charity, taking the dreadnought with him and leading a vast Covenant fleet to Earth. On Earth, the same dreadnought was used to activate a long-dormant portal, propelling Truth and his forces to the Ark.