Dugin sees the war as a type of "holy war" against evil which he sees embodied in Western civilization. Ergo, the war is aimed at removing this influence from Ukraine or at least parts of it, and the talk of a Russian "empire" is meant to indicate an alternative "empire" to the empire of evil which he sees spreading to Russia's borders.
It's not unlike Reagan and Thatcher's "empire of evil" rhetoric against the Soviet Union.