Gao

Gao, known to the Forerunners as Edod, is a remote human Outer Colony in the Cordoba system that survived the Human-Covenant War. While under the administration of the Unified Earth Government, the people of Gao maintain a strong sense of national identity and anti-UEG sentiments are commonplace. The planet's Montero region was home to a vast cavern system — in fact an artificial Forerunner construct designed to support the Maginot Line.

During the Insurrection, Gao openly supported the Insurrectionists. In 2553, a UNSC research battalion protected by Blue Team arrived at the planet to investigate a series of inexplicable miracle cures that had recently begun to occur within the Montero Cave System. At the same time, citizens of Gao were discovered in the cave system, having been brutally murdered. Special Inspector Veta Lopis of the Gao Ministry of Protection was assigned with investigating the serial killer. Her search led her to the possibility that the killer may be hiding within the Spartan ranks. As the situation turned into a crisis, politicians of Gao's planetary government, loyal to Insurrectionist groups, aligned with a dangerous Covenant remnant faction to prevent the UNSC from utilizing the Forerunner technology.

Trivia
The planet may be named after a city of the same name in Mali.

List of appearances

 * Halo: Last Light