Warhammer 40K: The Horus Heresy 

The 31st Millennium. For two long centuries, the Emperor of Mankind's Great Crusade has swept across the stars, reuniting long-lost human worlds and forging a nascent Imperium from the ashes of Old Night. After millennia of isolation, war, and barbarism following the Age of Strife, humanity was once more united under a single, glorious banner. Xenos empires were shattered, ancient evils quelled, and the glorious Imperial Truth championed across a thousand thousand worlds by the Emperor's twenty Primarch sons and their mighty Space Marine Legions. Peace, prosperity, and the promise of a golden age seemed within humanity's grasp.

But peace is a fleeting dream, and the architect of that unity, Horus Lupercal, Warmaster and favored son, now stands upon the precipice of an unimaginable betrayal. A chill wind sweeps across the stars, carrying whispers of heresy and the stench of nascent war. Brother turns against brother, legion against legion, as ancient loyalties are shattered and the very foundations of the Imperium begin to crumble. This is not merely a war; it is the Horus Heresy, the cataclysm that will forever scar the soul of mankind.

You are thrust into the grim darkness of M31, on the terrifying eve of the greatest civil war the galaxy has ever known. Will you stand with the Imperium, a bastion against the encroaching shadow of Chaos, or will you embrace the promises of a new, horrifying order, even if it means bathing the stars in fire? The fate of humanity hangs by a thread, and the galactic stage is set for an epic, awe-inspiring tragedy. The Eye of Terror beckons; what will be your legacy in its infernal gaze?