Installation 05

In the video game Halo 2, Installation 05, also known as Delta Halo (see footnotes), is one of the Halo "Fortress World" Installations built by the Forerunners to contain the Flood. It is also one of the rings that The Covenant is searching for – to control and activate them is required to complete their 'Great Journey'.

When the High Prophet of Regret fled New Mombasa, East African Protectorate (destroying the city in the process), he set up a Base of Operations on Delta Halo (Installation 05) to make the first attempt to activate it. Master Chief followed him there and assassinated him.

Delta Halo has submerged structures, ruins, and little-known wildlife. This Halo is the scene of many battles between the UNSC ,the Covenant, the Flood, and the Forerunner robots defending it . All three groups seek the Sacred Icon/Index and its Library is the home to the omniscient commander of the Flood, Gravemind.

When the High Prophets and the Brutes betrayed the Elites, the Brutes set up a Base of Operations in the Control Room of this Halo, in order to activate the Installation, while the High Prophets' Forerunner flagship headed for Earth in search of the Ark.

The uneasy UNSC-Covenant Separatist alliance launched an offensive against the Brute encampment, and the Arbiter killed the High Prophets' Brute Chieftain Tartarus. The Index was retrieved, thus shutting down Delta Halo activation. However, this situation sent signals to other Halo Installations, and become ready for remote activation from a core installation known as The Ark.

Halo 3 will presumably pick up where this storyline leaves off. The fate of Delta Halo is unknown.

Although "Delta Halo" is the title of only a specific group of levels in the Halo 2 campaign set on the second Halo installation, Delta Halo is, in fact, the UNSC designation for the Halo installation in Halo 2. Contrary to some assertions, the name does not refer to a river delta on the Halo structure. This is evidenced in the in-game description of the multiplayer map "Ascension" and the official online description of another multiplayer map, "Containment".