The UNSC Pillar of Autumn (C-709), also known as the Autumn, is a Halcyon-class light cruiser in the UNSC Navy.
Prior to the Fall of Reach, Pillar of Autumn was selected to support Operation: RED FLAG, a SPARTAN-II operation to capture Covenant leaders. Captain Jacob Keyes was placed in command. The operation was forestalled by the Covenant assault on Reach and the cruiser was one 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 AI 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 Flood. The ship's sole remaining combat effective SPARTAN-II, John-117, was forced to detonate Pillar of Autumn's fusion reactor, destroying the ship and the installation to prevent the installation from firing.
The Battle of Installation 04
- Main article: Battle of Installation 04
Pillar of Autumn was immediately engaged upon arriving at Threshold. The cruiser was spared destruction by the Prophet of Stewardship who feared stray Plasma Torpedo fire might damage Installation 04. So the Covenant made to board and capture the ship instead. Pillar of Autumn destroyed four ships and damaged Truth and Reconciliation before boarders disabled its Magnetic Accelerator Cannon with an Antimatter charge.
Captain Keyes ordered the crew to abandon ship. John-117 was given Cortana for safekeeping, and ordered to keep the AI out of enemy hands as part of the Cole Protocol. The crew left the ship for the ring in whatever craft were available and the cryo pods were jettisoned. Keyes directed Pillar of Autumn on a course to crash land on the ring. The Covenant finally began hitting the ship with plasma torpedoes, but the cruiser survived the landing reasonably intact. The survivors would later transfer supplies from the ship to Alpha Base.
The release of the Flood added an unexpected dimension to the battle. Monitor 343 Guilty Spark was preparing to fire the installation in response to the outbreak; in conjunction with the entire Halo Array this would wipe out all sentient life in the galaxy. John-117 and Cortana returned to Pillar of Autumn to destroy the ring by detonating the still-functioning fusion reactors. An attempt to activate the cruiser's self-destruct from the bridge failed due to 343 Guilty Spark's interference. The Spartan was forced to manually destabilize the reactors with tactical ordnance.
The Spartan and AI escaped the subsequent detonation and the ring aboard a Longsword fighter still docked in Launch Bay 7. The effort to destroy Halo with Pillar of Autumn succeeded, sparing the universe from the Flood and a Halo activation.
Pillar of Autumn was roughly 43 years old at the time of its escape from Reach and its later destruction on Installation 04. It was a cruiser of the Halcyon-class, the third largest in the UNSC Fleet at the time. Like other Halcyon ships, Pillar of Autumn was equipped with a honeycombed internal bracing structure that allowed it to function even after sustaining critical levels of damage.
Pillar of Autumn was refitted with an improved nuclear fusion engine that supported the two smaller existing reactors around a newer larger one, which were capable of boosting the overall power output by 300% for a short time if needed.
Fusion reactors generate extreme heat which must be removed in order for them to remain active without overheating. The Autumn's overhauled reactors were an especially severe case of this. Usually, the excess heat was conducted to a chemical agent which would then vent into space. However, Pillar of Autumn's upgraded specifications also included an upgraded cooling system, which featured a "laser-induced optical slurry of ions chilled to near-absolute zero," which is far more efficient than the typical method and removed the reliance on expendable chemical temperature-control substances. In essence, the amount of excess heat removed by the new system increased as the reactors' output did. This self-regulating and self-cooling power plant was critical in combat since it virtually eliminated a commander's concerns about overheating and slagging a ship's engines. Pillar of Autumn's reactor was able to be overloaded by explosives, either grenades or rockets, destroying the vulnerable vent cores. Once these were destroyed, the reactor began to go critical, resulting in temperatures of over 100,000,000 degrees and a thermonuclear explosion large enough to tear apart a Halo Installation.
- Pillar of Autumn is the first UNSC ship in all the Halo games that you are able to explore the inside of.
- On the first level of Halo SPV3, the bulletin board just outside the bridge of the ship contains 4 interesting and even amusing facts about the development of the mod such as:
- "RIP Impaler and destroyable tress :( " Which references to the cut weapon and that trees at one point were destroyable
- "Keyes's face sucks"
- "Lightmaps and Terminals make Masterz a dull boy" Which references to how much time and effort Masterz and his team put into them
- "Those traumatized please seek medical health"
- In Halo SPV3, the ship's official emblem was changed to the Seventh Column logo as seen in the bridge and on Captain Keyes' ID Patch
- Though on the Bulletin boards, it is still the Marathon logo