Covenant citadel

The citadel is a Covenant base structure, and the Covenant equivalent of the UNSC Firebase in Halo Wars. It contains a Command Center, seven building sites, and four turret foundations.

When a new base has been claimed in standard Skirmish or multiplayer mode, the beginning base facility is called the Outpost. It includes a Command Center and three building sites, but no turret foundations. Outpost can be upgraded to a Keep, which includes a Command Center, five building sites and four turret foundations, and can be upgraded to a citadel.

Summary
The citadel is a basic command structure with defenses such as Wraiths, Ghosts, and Banshees, and can also be defended by base turrets. It also has a similar underground garage to the UNSC's Firebase. These provide field command facilities for invading or defending Covenant Armies. Much like its UNSC equivalent, it possesses 7 expansion "sockets" for more structures for research, unit production and defense.

The available buildings that the citadel can provide are a Hall, Temple, Factory, Summit, Shield Generator, and a Warehouse. It is colored a deep purple, like most Covenant buildings, vehicles, and ships.

Expansions

 * Temple
 * Warehouse
 * Hall
 * Factory
 * Summit
 * Shield generator
 * Automated plasma turret

Units produced and available upgrades

 * Scarabs
 * Honor Guard Elites (Prophet of Regret only)
 * Cloaking Ability
 * Personal Shield
 * Brutes (Brute Army Commander only)
 * Jump Pack
 * Electric Shot
 * Suicide Grunts (Arbiter only)
 * Zeal
 * Defile

Trivia

 * Unlike the Firebase, the Citadel's buildings seem to be built by an orbital beam. The UNSC constructs their buildings underground.
 * In "Origins II", at the moment when the Covenant and humanity fight together against the Flood, one can see a Summit and a Citadel consumed by the Flood.

List of appearances

 * Halo Wars
 * Halo Legends
 * Origins
 * Halo: Blood Line