To those participating, a void war seems a terrifying, roiling chaos of violence, but it is the pinnacle of mankind’s destructive ingenuity, a whirl of gigantic explosions where lives are snuffed out by the hundred. In such combat, a single man is nothing; he is but part of the machine of the ship he serves, as essential or otherwise as a steel cog or an indicator lumen. He can do nothing but work his appointed task and pray his life will not end, or if it must end, that it does so in painless disintegration. A single crewman’s task dominates everything, even his fear of death. There is no escape from service. War and his part in it are the totality of his existence.

Yet what is a void war to the timeless deeps of the blackness that envelops all these footling motes of light that sentient creatures battle so earnestly over? A void war is twinkles in the distance. It is silence. It is infinitesimals of matter sparking and dying, scintillas of metal and flesh consumed by transient fires. The detonation of a battleship kilometres long is insignificant to a cosmos where the death of a sun atomises worlds. On a galactic scale, the loss of a warship and ten thousand lives is a nugatory flash outshone by the billion-year candles of the stars.

The inverse is true to a single man. His life is all that matters, for one life is all a man has, and he fears to lose it. Yet he must blindly serve in terror. The universe gives meagre gifts, and it does not care how they are spent.

Over Thessala, mankind fought in a civil war already centuries old. The Emperor of Mankind, a human with the power of a god, had tried and failed to unite humanity’s scattered worlds so that the species might survive the supernatural threat of Chaos. His sons, the primarchs, godlike beings He had created to complete this task, had themselves been corrupted, and half had turned against Him. The Horus Heresy, that war was called. It had ended the Emperor’s dream.

The Heresy was part of a war that had continued for aeons and would continue for aeons still.

To the beings of this galaxy, the war was everything; to the blank gaze of time, it was nothing. And yet, for all humanity’s seeming inconsequence, the children of its greatest son held the fates of two realities in their careless grasp.