here would be no Imperium without the Emperor's Great Crusade. After the Warp storms died down in the 30th millennium, the Emperor gathered his recently created Space Marine Legions and launched his Great Crusade to reunite the isolated and scattered human settlements across the galaxy.

The Legions battled on thousands of worlds to liberate them from the tyranny of aliens or traitors to Mankind. These Apocalyptic battles are shrouded in legend, but by the end of them, the Emperor ruled a realm of over a million worlds and innumerable Humans. He organized them into the Imperium and prepared them for the struggles to come.