UNSC Pillar of Autumn (Earth-2915)

"There was only one ship. One? Are you sure? Yes. They called it the Pillar of Autumn."

- Thel 'Vadamee and the High Prophet of Truth

UNSC Pillar of Autumn, (hull classification symbol C-709), was a Halcyon-class light cruiser in the UNSC Navy. It was informally referred to as the Autumn, and, in some cases, the Pillar. It was the sister ship of the UNSC Toulouse.

Prior to the Fall of Reach Pillar of Autumn was selected to support Operation: RED FLAG, a SPARTAN-II mission 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 Soell system by the auton synthetic Cortana. There it was engaged by a Covenant fleet guarding Installation 04. Keyes crash-landed the ship on the installation where the surviving crew continued the battle against the Covenant, and later, the xenomorphs. The ship's sole remaining 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.

Source

 * https://www.halopedia.org/UNSC_Pillar_of_Autumn.