|“||I am a monument to all your sins.||„|
Gravemind is a parasitic hive-mind intelligence and the leader of The Flood. It is one of the main antagonists in the Halo series, serving as a supporting antagonist of Halo 2 and one of two main antagonist in Halo 3 (alongside the Prophet of Truth).
The first known Gravemind came into existence as a centralized intelligence to coordinate Flood efforts against the Forerunners, formed from the mindsin their insanity, found it to be a serendipitous emergence and began to guide and feed its growth. It is indicated that the remaining Precursors became the Flood fully, to a lesser or greater extent. Mendicant Bias intentionally became rampant, developed a hatred for his creators and actively worked toward their destruction. The Gravemind utilized a 'Logic-Virus' to subvert other AI's, and may be how he converted Mendicant Bias to his cause originally.
The Forerunners developed a new AI, Offensive Bias, which coordinated the final battle against Mendicant Bias and the Flood. The Gravemind was destroyed or stopped by the first activation of the Halo rings.
Gravemind later used the UNSC In Amber Clad to board the Covenant Holy City High Charity, crashing the frigate into a city wall and releasing numerous Pelicans full of the Flood plague. Within days, he took over the entire city, and all life within it.
As John traveled deep into High Charity, he faced multiple Flood forms and heard the Gravemind taunt him, allowing Cortana to briefly send pained messages as he corrupted and tortured the UNSC AI. The Gravemind became increasingly frustrated at the Spartan's progress, becoming suspicious of what Cortana was hiding from him and threatening to "feast upon [John's] bones" if she didn't reveal the secret.
After John rescued Cortana, the Gravemind became enraged, realizing that she planned to use the incomplete Halo to destroy him. He attempted to kill them both, but failed, and John successfully destroyed High Charity, presumably killing the Gravemind. After traveling to Installation 04B, however, John discovered that the Gravemind was attempting to rebuild himself on the new Halo. The Gravemind ultimately failed to stop John from activating the ring and destroying him, at least for the time being.