The Arsenal is the upgrade from the Barracks offering two new units. It still focuses on Manpower cost for units, with Energy being the new focus as well. THe structure now houses the Hover Tank and Black Queen. This is the final upgrade available for the Outpost line of structures.
The Arsenal allows for the construction of Hover Tanks, easily one of the most powerful ground units in the game. It also features the Black Queen, a game-changing unit that can change the battlefield in ones favour.
With a proper set of resource generation buildings, it is possible to pump out many Hover Tanks which with proper micro is easily one of the most dangerous ground units available, even outmatching the Sakata Spider.
A name that should put fear into your mind, as this unit will annihilate most ground units in one shot and do decently in air-to-air combat. Although this unit is powerful, it must still be used mindfully!