Overlord Citadel

 is a building of the Overlords.

Background
It costs 4000 Resources to upgrade from a Stronghold, if an Academy and Garage already exist. The Citadel holds 30,000 Resources, 100 Butanium, and 100 Supplies. All valid units may receive extended training here. This structure is required in order to obtain a Bio-Wing, Arcanery, and Communications Antenna.