The UNSC Pillar of Autumn, (hull classification symbol C-709),^[5][6] was aHalcyon-class light cruiser in the UNSC Navy. It was informally referred to as theAutumn, and, in some cases, the Pillar.^[7][8][9]


Prior to the Fall of Reach the Pillar of Autumn was selected to supportOperation: RED FLAG, a SPARTAN-IImission to capture Covenant leaders.Captain Jacob Keyes was placed in command. The operation was forestalled by the Covenant assault on Reach; the cruiser carried some of the few UNSC survivors and fled the system having lost most of its intended SPARTAN-II passengers.


The cruiser was guided to the Soellsystem by the AI Cortana. There it was engaged by a Covenant fleet guardingInstallation 04. Keyes crash-landed the ship on the installation where the surviving crew continued the battle against the Covenant, and later, theFlood. The ship's sole remaining combat-effective SPARTAN-II, John-117, was forced to destabilize the Autumn's fusion reactor, destroying both the ship and the ringworld, to prevent the Installation from being fired.