From Halopedia, the Halo wiki
During the attack on the Capital, Purpose made his way to one of the ships in the equatorial ring. Along the way he locked a crowd of panicked Forerunners out of the hangar believing they were a danger. There he recorded a warning to any attempting to rescue him to stay away, that nothing could be done because there was not enough time. He noted the casualties caused by the mass panic from the battle, he warned others to leave before the Halo Array was fired. Over a century after the Halos' firing, several Forerunners had returned to Maethrillian to repair the Domain, the IsoDidact among them. While looking for ships to leave the Milky Way galaxy with, the group came across Purpose's recording. Before hearing the entire recording, however, the Precursor construct, Abaddon, cut off power to their ship, prematurely ending the recording.
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