The Age of Strife was mankind's long night, an era of some five thousand years in which the fragile human realm collapsed into isolation and madness. Warp storms of unprecedented ferocity engulfed the galaxy, severing every world from every other and rendering interstellar travel a suicidal gamble against the raging Immaterium.
Across this dark age the human psyche began to blossom with witch-power, and with it came ruin. Rogue psykers birthed daemons in their waking dreams, whole worlds were consumed by warp-spawned horrors, and the newborn Dark Prince of pleasure stirred in the depths as the Aeldari empire drowned in its own excess. Isolated from aid, humanity's scattered colonies fell to xenos raiders, tyrant-kings, and abominations without number.
Amid this chaos the knowledge-hoards of old were shattered or forgotten. What technological lore survived was clutched by secretive cabals and tech-priests whose successors would one day found the Adeptus Mechanicus upon Mars, preserving fragments of a greatness they could no longer comprehend.
Yet in the shadows a single figure laboured. Upon ancient Terra the Emperor gathered strength and armies, uniting the shattered techno-barbarian tribes of the cradle-world and preparing the gene-forged sons who would carry His light back to the stars. When at last the storms began to calm, mankind stood upon the threshold of either final extinction or a new dawn.