Keyes crash-landed the ship on the installation where the surviving crew continued the battle against the Covenant, and later, the Flood. There it was engaged by a Covenant fleet guarding Installation 04. The cruiser was guided to the Soell system by the smart AI Cortana. 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.

Captain Jacob Keyes was placed in command. Prior to the Fall of Reach Pillar of Autumn was selected to support Operation: RED FLAG, a SPARTAN-II mission to capture Covenant leaders. The ship's motto is Ad Arcendam Hostium ( To Repel the Enemy). It was the sister ship of UNSC Dawn Under Heaven and UNSC Toulouse. It was informally referred to as the Autumn, and, in some cases, the Pillar. UNSC Pillar of Autumn, ( hull classification symbol C-709), was a Halcyon-class light cruiser in the UNSC Navy. ' - Conversation between 'Vadamee and the High Prophet of Truth. Thel 'Vadamee: ' There was only one ship.' High Prophet of Truth: ' One? Are you sure?' Thel 'Vadamee: ' Yes. 8 Mark 33 Spitfire naval coilgun batteries.4 Shiva-class nuclear missiles mounting 30 megaton HAVOK warheads.Titanium-A battleplate (several meters thick) Kawanishi Engineering's SED-2550X (Series V CODEN) Post-refit: Experimental reactor set (1 primary, 2 secondary).Pre-refit: Mark II Hanley-Messer DFR (3).Boglin Fields' Starfire-IV fusion rockets.For the longsword variant, see C709 Longsword.

Halo pillar of autumn canyon