The very act of being exposed to the Precursors minds within the Gravemind drove the Ur-Didact to a brooding, hate-filled insanity. The Precursors, insane, but driven by a need to create new life, decided that the Flood would be their instrument all life they made from then on would know only suffering, and would never have the chance to throw down their makers ever again. The remaining Precursors, driven to insanity by the betrayal of their creations (the Forerunners) instead embraced the disease they had accidentally birthed, guiding it to cease infecting humanity as if they had successfully immunized themselves. Over the Eons, however, the dust became flawed and corrupt rather than rebirthing the Precurors as they were, it only brought a cancerous plague and death. The dust that humanity had discovered that led to the birth of the Flood threat was one of the failsafe measures the Precursors put into place to try and avoid their extinction. It was later revealed that the Flood was not a creation of the Precursors, but the Precursors' perverted and insane remains of themselves. The Flood/Precursors found humanity worthy of the Mantle and instead traveled to take revenge against the Forerunners. The Flood attacked humanity for only a short while because the Precursors favored humanity. Some Precursors hid in stasis while others changed into the dust found by the ancient humans (the latter created the Flood). They were annihilated by Ancient Forerunners, who wished to seize the Mantle of Responsibility from the Precursors instead of letting them give it to Humanity. However, in Halo: Silentium the Flood is revealed to be another form of Precursor made via the powder referenced to in Halo: Cryptumthat was also revealed to be actual Precursor desiccated remains. If so, then they were entirely successful.

The fact the Gravemind considered itself a Precursor implies that the Precursors created it for revenge against the Forerunners. The Primordial, a Gravemind that identified itself as the last Precursor, revealed that the Precursors had been ruthlessly killed in a war with the Forerunners millions of years before the events of Halo and that 'their answer is at hand' - implying that a proto- Flood form (described as a fine dust contained in hundreds of glass cylinders) was created as revenge or as a failsafe. They expected them to continue their work after they departed-the same way that Forerunner lifeworkers (including the Librarian, or the Lifeshaper) viewed Humanity before the activation of the Array. The Precursors presumably viewed the Forerunners as their own legacy.

The logs stored in the Terminals around the Ark record that the Forerunner ' Mantle' (Guardians of the Galaxy and all life) may have been handed down from 'legends of the past,' the Precursors.

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