- "This one, Cleyell, was recent. They hit the only city left on the planet. Those folks made it all the way through the war… for this."
- — An Orbital Drop Shock Trooper
During the Human-Covenant War, Cleyell was attacked and partially glassed by the Covenant. However, the United Nations Space Command was evidently able to repel the Covenant forces, though only a single city on the planet survived the Covenant's assault. Cleyell remained untouched for the remainder of the Covenant War and the colony's remaining population continued to live on the planet.
Following the Covenant War, although the Covenant had been dissolved, Cleyell was attacked in 2556 by a remnant of the former alien empire who subsequently glassed the remaining city on the planet. With hostile Kig-Yar raiders scavenging Cleyell's surface, the survivors contacted the Unified Earth Government for assistance. In response, the UNSC launched a massive rescue operation to Cleyell that included UNSC Marine Corps' Orbital Drop Shock Troopers and elements of the UNSC Army's 412th Engineer Command aboard UNSC Cascadia. After arriving at Cleyell, upon the suggestion of Sergeant Holly Tanaka, a lieutenant commander aboard Cascadia deployed Army and Marine search-and-rescue teams to rescue the stranded colonists on the surface, rescuing dozens of colonists from death or enslavement at the hands of the Kig-Yar.
A D79-TC Pelican flying over Cleyell's glassed surface
List of appearances
- Halo: Escalation (First appearance)