Which Halo game introduced the Promethean enemy faction?

Halo 4 introduced the Promethean enemy faction. These Forerunner combat constructs appear as enemies when Master Chief and Cortana explore the Forerunner world Requiem.

The Prometheans include classes such as Crawlers, Watchers, and Knights. They serve the Didact, a powerful Forerunner figure who opposes humanity and considers humans an existential threat. Their combat style differs from that of the Covenant: Promethean units use hard-light technology, teleportation, shields, and mechanical support drones.

Halo 4 also introduced weapons associated with the Prometheans, including the Binary Rifle, Incineration Cannon, and Suppressor. Players sometimes use “Promethean” to describe only the Knights, but the term covers the wider faction and its combat machines. Halo 5: Guardians and Halo Infinite later expanded the faction and its relationship with other Forerunner technology.