The Covenant leadership discovered Humans could interact with Forerunner technology, and decide to destroy humanity in order to suppress this fact. The Forerunners were forced to activate the Halo network, killing themselves and any potential Flood hosts, in an effort to starve the Flood to death. During the course of the game, players discover that the Halos were built as a weapon of last resort against the Flood, an extragalactic parasite which is driven to consume all sentient life.

The massive installation was built by an enigmatic race known as the Forerunners, who have long since disappeared the Covenant worship the Forerunners as gods. In the 2001 video game Halo: Combat Evolved, the UNSC ship Pillar of Autumn discovers a mysterious ringworld known as ' Halo'. Halo 's story has 26th century humanity, led by the United Nations Space Command (UNSC), caught in a war with an alien coalition known as the Covenant. The Halo video game and media franchise takes place in a fictional universe, where there are four major factions players encounter or control.

Halo marine concept art