Unidentified ancilla (Shield World 0459)

"Security barrier breached, high order infection detected, unidentified alien intrusion detected, initiating Stage 3 Defense Protocols."

- When SoF enters the Shield World

An Unnamed Forerunner AI was a construct located on the Flood-Controlled Shield World.

History
It is unclear whether it is in charge of the whole Shield World or just the Cleansing Rings When the Spirit of Fire went into the underground section, it detected a "high order" Flood infection and an unknown alien intrusion. Once he detects these he initiates "Stage 3 Defense Protocols", which included activating Sentinels, cleansing rings, and Super Sentinels to clear away the Flood and the "unknown alien intrusion". Every time the Spirit of Fire approaches a cleansing ring it will say "Decontamination sequence commencing".

Trivia
The AI's voice does not resemble that of any other known Forerunner AI. While AIs like the monitors have a relatively normal voice, this construct speaks in a robotic monotone. It's seemingly a what could be classified as a "dumb" AI, as it seems to only follow a strict protocol and doesn't even take note of the presence of intruders such as the Covenant or even "reclaimers", unlike the monitors. This is interesting, as it's guarding one of the most valuable installations built by the Forerunners.