What is the Horus Heresy about
Sometimes poetically referred to as the "Age of Darkness," the Horus Heresy was a galaxy-spanning civil war that consumed the worlds of humanity for 9 Terran years. Its eruption marked the end of the Emperor of Mankind's great crusade to reunite humanity's scattered colony worlds in the Milky Way under a single government, and the beginning of the present Age of Empire. The Horus Heresy is in many ways the founding event of the empire of mankind as it now exists.
The Civil War began after the corruption of Imperial Warmaster Horus Lupercal, primarch of the Sons of Horus Legion and the Emperor's most beloved son, by the corrupting forces of Chaos. The Chaos Gods nurtured Horus' innate ambition and sense of treachery at the hands of the Emperor until he turned on his father and attempted to claim the human empire for himself.
Horus convinced half of the other Space Marine Primarchs and Legions, as well as much of the Imperial Army and the forces of the ancient Mechanicum, to enlist Traitor at his side and launch a disastrous attempt to conquer the galaxy in his name.
War raged for 9 Terran years, 7 of them consumed by Horus' assault on the Throne World, culminating in a final cataclysm on Terra itself, where Horus was killed and the Emperor mortally wounded. His dreams of creating a better future for mankind were shattered forever. The conflict was fought across the Milky Way at the beginning of the first century of the 31st millennium and resulted in more than 2.3 trillion deaths, 4.6 trillion if you include the planetary populations killed by the Imperium after the heresy due to the corruption of the chaos have been cleaned up.
The heresy ended with the death of the traitorous Warmaster Horus, the imprisonment of the Emperor on the Golden Throne, and the exile of the heretical Astartes Traitor Legions into the Eye of Terror. Heresy was directly responsible for the birth of the present structure of the Space Marine Chapters after the Second Foundation and the reorganization of the Empire by the Ultramarines Primarch Roboute Guilliman as Lord Commander of the Empire and Imperial Regent during the 31st Millennium Time of Rebirth.
While the following account is very detailed, it should be noted that much of this information was completely unknown to the average denizen of the 41st Millennium Empire.
The Horus Heresy occurred over ten thousand Terran years ago, an almost unimaginable length of time; As a result, for the average Imperial citizen, it has become nothing more than a collection of often distorted or misunderstood legends and mythologies.
When the implications of the deification of the Emperor, the theological needs of the Adeptus Ministorum, and the outright erasures and falsifications of Imperial history by the Inquisition are thrown into the equation, the truth of the events surrounding the Horus Heresy could prove very shocking in the Deed to the people of the Empire.
The game Horus Heresy
The Horus Heresy has been a part of Warhammer 40,000 since its inception, and while the story has undergone more than a few changes over the years, it remains a cornerstone of the history of the galaxy. So much so that over 100 books, novellas and short stories have been written about its events.
It's clear that much of the enduring love for the Horus Heresy comes from the Legions themselves, as the sheer variety of characters between them ensures there's a home for hobbyists of all stripes. The new edition reinforces this trait with characterful rules for all 18 legions, allowing players to create a force that best represents the factions they know and love.
Though the conflict involves millions of soldiers, titanic war machines, and the clashing of fleets on an unimaginable scale, the drama of heresy is also written on a much smaller scale - relationships between individual characters. These play out on the gaming table just as they do in the books, as iconic characters like Abaddon and Garviel Loken re-enact their fateful Encounters.