From Halopedia, the Halo wiki
Monitor 01-001 was a Forerunner-created ancilla designated as the caretaker of Installation 01.[Note 1] The nomenclature describing them denotes their position as it relates to the first ring and its name was meant to represent both an omen and an epitaph for Forerunner civilization.
Near the very end of the Forerunners' war against the Flood, this monitor was commissioned alongside six others in order to oversee the Neoteric Halo Array, with Installation 01 in particular being placed in this monitor's charge. Right before the Halo rings were dispersed from Installation 00 in its place beyond the rim of the Milky Way, all seven monitors convened aboard a vessel known as the Lifeworkers' crèche. There, they were certified as being fit for their duties, the first of which would be the preparation of activation indexes, distributed to each, for each installation. The IsoDidact and a handful of Lifeworkers gathered with this monitor and the six others within the ship's command center before the final dispersement of the Array. Thereafter, this monitor was relocated to Installation 01 within the galaxy's Orion Arm, the furthest Halo from the Ark.
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