Mendicant Bias was a Forerunner Contender-class ancilla, created to serve as the central Forerunner intelligence in defense against the Flood prior to the start of the Forerunner-Flood War. It was created by both the Master Builder and the Didact, who held competing ideas on the best strategy for combating the Flood, but worked together to build the most powerful AI ever created by Forerunners in Mendicant Bias. After the Didact plan for shield worlds lost out to the Master Builder’s halos, forcing the Didact into hiding, Mendicant Bias was put in charge of the Halo Array. During testing of one of the halos, Installation 07, at Charum Hakkor, the Primordial was released from stasis and brought to the halo for interrogation, where it corrupted Mendicant Bias, turning it against the Forerunners and taking the halo with it.
Years after Mendicant’s subversion by the Flood, the AI, along with the Primordial, brought their halo to the Forerunner capital of Maethrillian, where they used it in the Attack on Maethrillian, firing the halo and killing everyone on the capital world. Afterwards, Mendicant assisted the Primordial in studying the Flood’s affect on the humans who lived on the ring, though their efforts were eventually put to an end by the IsoDidact, who killed the Primordial and decommissioned Mendicant Bias.
Later in the Forerunner-Flood War when the Flood had conquered most of Forerunner space, Mendicant Bias was reassembled by the Flood and the Gravemind, and was reinstated with the goal of destroying all Forerunners. The AI led the Battle of the Greater Ark which destroyed the remaining Forerunner defenses, and sent the Flood forces towards the Lesser Ark, though they were stopped by the firing of the Neoteric Halo Array. After the firing of the array and the destruction of all life in the Milky Way Galaxy, the IsoDidact captured Mendicant Bias again, this time imprisoning him on the Lesser Ark. Although Mendicant was no longer under the control of the Flood and again sided with Forerunners, the AI was left on the Lesser Ark, while the remaining few Forerunners left the galaxy.
Millennia later, a shard of Mendicant Bias was found by the San’Shyuum aboard the Forerunner Dreadnought at the heart of High Charity. This shard was consulted periodically by the prophets, using its cryptic responses as the basis for starting the Human-Covenant War. During the Battle for Earth in 2552, Mendicant Bias was sent back to the Lesser Ark along with the rest of the Forerunner Dreadnought, reuniting with the rest of its parts on the Ark. On the Ark, Mendicant interacted with Master Chief Petty Officer John-117 during the Battle of Installation 00 via terminals on the facility, though he has not been seen from since the firing of Installation 08 at the end of the conflict.