Home to the Apocalonites, it was discovered by the UNSC in the year 2579. The ship that discovered Apocalon was destroyed shortly after by an unknown force. The UNSC sent a group of ships to investigate. They came into contact with the Apocalonites, who they discovered were a vastly superior force. Several battles between the two groups, with eventual assistance from the Sangheili, resulted in the defeat of the Apocalonites. Shortly after, the Apocalonites asked for an alliance with the two, seeing that they would fall if the continued the war. After some hesitation, the Apocalonites offer was accepted. They quickly became allies of the Sangheili and UNSC. They currently are on good terms with the groups, and have compensated the UNSC for the damage they caused. Apocalon remains under the Apocalonites control. Although the atmosphere is alomost 80% oxygen, no life besides the Apocalonites exists, and the planet's surface is a barren wasteland.