From Halopedia, the Halo wiki
A Facilitator-class ancilla is a type of ancilla created and employed by the Forerunners. Ancillas frequently serve as sub-monitors for installations of the Halo Array, working for the facilitation of Array requirements. Facilitator-class ancillae may also be referred to as executors.
Facilitators are sometimes referred to as "adjutant monitors", reflective of their naming scheme of Adjutant [X], with the [X] taking the form of a random adjective. They are formed from the minds of living Forerunners rather than being created from-scratch as a full artificial intelligence (as in the case of Adjutant Revendicate), though are somewhat limited in their capabilities when compared to other ancilla classes such as the Caradon-class and Archeon-class - or even full monitors.
Facilitators are typically assigned specific subsystems of a given installation - such as a Cartographer - to keep watch over. Should the installation's monitor become unfit for duty, the sub-monitor takes over and resumes their functions (albeit in a limited capacity). Sub-monitors may also serve as station attendants, rail attendants and manage other administrative and custodial functions. Adjutants may also serve as a core component on Forerunner starships; for example, the Supernal Spiral-class keyship Anodyne Spirit maintained 560 adjutants alone.
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