Unnamed Forerunner A.I

"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 on the Flood-Controlled Shield World. 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"