It is revealed in World of Warcraft: Illidan, that Argus [home of the peaceful Draenei] is in fact intact, and is the "beating heart" of the Legion's forces with all its greatest commanders and Kil'jaeden using it as his seat of power. The entire world has been corrupted into a shadowy version of what it once was. The machines that originally were used to send out peaceful and healing waves of magic over the surface, have been inverted to spread fear, depression, and panic. The capital city of the planet which is unnamed is the current seat of Kil'jaeden and is perhaps one of the most magically protected locations in the universe, with Kil'jaeden himself presiding over the Burning Legion from the palace throne.
The Republic is the Empire.