Pillar of Autumn (Earth-2042)

"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 GRSC Navy. It was informally referred to as the Autumn, and, in some cases, the Pillar. It was the sister starship of the Toulouse.

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

The cruiser was guided to the Threshold system in the Soell sector by the AI Cortana. There it was engaged by a CIS 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 Flood. 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.

Galactic Republic-Covenant War
Pillar of Autumn was constructed on Coruscant. The ship began construction in 59 BBY, was completed in 57 BBY, and was launched on 56 BBY.

Battle for Arcadia
During the Battle for Arkai in 49 BBY amidst the Republic-Covenant War, Pillar of Autumn engaged two CCS-class battlecruisers alongside three other Halcyon-class light cruisers. Along with the other three ships, Pillar of Autumn destroyed a battlecruiser after catching it with its shields down, but another battlecruiser was able to make it to the surface of Arkai. In the battle between the GRSC and Covenant forces, Pillar of Autumn was badly damaged along with the other cruisers were destroyed. Upon the arrival of the Spirit of Fire, the AI Serina reported on these events to Captain Jin Cutter. Later in the battle, at the request of Spirit of Fire, Pillar of Autumn contributed several M808B Scorpions to the ground battle, enabling Spirit of Fire's forces to take down a Covenant energy shield.

Source

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