The Empire of Darkness was, if you couldn't tell, an Empire. It was originally the primary antagonist of Bionicle: The Next Chapter, but it became more background after more powerful villains were introduced en masse. They are bent on conquering as much land as they can, mostly through military action.
Velika founded the Empire shortly after he eliminated most powerful beings on Spherus Magna. Automatically it set its eyes on conquering New Atero, the giant metropolis. It was the ultimate symbol of recovery and good's triumph over evil. If the new evil conquered it, how poetic it would be, and quite an accomplishment. The Empire was