Name: The Custodian
Species: Forerunner Ancila (Contender Class, Metarch-Level AI)
Age: ~100'000 years
Faction: Forerunner
Alignment: Chaotic Neutral
Status: Online
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Strengths
N/A
Weaknesses
N/A
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Equipment
Unknown. Presumably some sort of central hub from which it is connected to every piece of Forerunner technology in the Milky Way Galaxy.
Powers
As mentioned before, The Custodian practically has control over every piece of Forerunner technology in the Milky Way Galaxy. Where it is located is unknown, however it can be assumed that The Custodian runs on advanced supercomputers that communicate information through slipstream space (faster than light warp-space) due to its seeming ability to monitor and control multiple Forerunner constructs at once seamlessly without any delay.
History
Absolutely nothing is known about The Custodian's history. However some data logs pulled by UNSC AI Sheila from the Core Room Antechamber during the final moments of The Battle of Haven may have revealed some clues explaining the nature of the Ancila. The Custodian is a Contender Class AI, which is by far the most advanced type of AI known to be made by the Forerunners. Furthermore, The Custodian is a Metarch-Level Ancila, meaning that it has full control of all other AI networks beneath it; effectively giving it control over all Forerunner constructs in the modern day.
This extremely powerful Forerunner AI was thus responsible for the final events of The Battle of Haven, specifically during the planet's lockdown, suspension and increase in sentinel production.