The Composer is a Forerunner device used to reduce a living being into a collection of data – referred to as an "essence" by Forerunners.
A Cryptum is a Forerunner stasis/containment machine used to safely preserve beings in a state of meditation for incredibly long periods of time.
Guardians are powerful security constructs created by the Forerunners to enforce the tenets of the Mantle for the greater good of the galaxy.
The Halo Array is a series of ringworlds created by the Forerunners for the purpose of destroying the horrific extragalactic parasite known as the Flood.
The Janus Key is a Forerunner device which acts as an activation catalyst for a galaxy-spanning Cartographer within a site called the Absolute Record.
Promethean Crawlers are low-grade, quadruped constructs created by the Forerunners.
Promethean Watchers act primarily as defensive drones, taking on a tactical support role.
Promethean Knights are a series of heavily armored, powerful biped machines operated by sentient essences cultivated via the Composer.
Soldiers are Armiger-class bipedal combat platforms developed and employed by the Forerunners. These war-machines proved incredibly useful for raiding ancient human warships and combating the Flood.