From Halopedia, the Halo wiki
The factory is a Covenant structure featured in Halo Wars. The factory is where the player can build Type-32 Ghosts, Type-25 Choppers, Type-26 Wraiths and Shua'ee-pattern Locusts. All the land-based vehicle upgrades are researched in the factory as well.
The Covenant are able to build the factory from the beginning of the game, without needing any upgrades on the Citadel first. The vehicles built here are prone to an air attack. Like the Covenant Hall and Summit, it costs 150 resources and requires no tech level.
Units Produced and available upgrades
List of appearances