The Infinte Empire is as big as the Imperium

• 8th Ed Codex [Necron]”:

"What the Imperium cannot know is that, should the Necrons ever fully wake and unite, they would face a foe as numerous as themselves. For now, the galaxy has had but a taste of the dynasties’ destructive potential, and it is fortunate for their foes that the Necrons remain divided by madness and conflicting agendas. However, these are but the first stumbling steps of a giant as it gathers pace, and even now powerful leaders like Anrakyr the Traveller, Imotekh the Stormlord and the Silent King are uniting their people under a common cause."