In the wake of the Dropsite Massacre at Isstvan V, the survivors of the Salamanders Legion searched long and hard for their fallen primarch, but to no avail. Little did they know that while Vulkan might have wished himself dead, he lives still...languishing in a hidden cell for the entertainment of a cruel gaoler, his brother Konrad Curze.

The Shadow Crusade has begun. While the Ultramarines reel from Kor Phaeron's surprise attack on Calth, Lorgar and the rest of the Word Bearers strike deep into the realm of Ultramar. Their unlikely allies, Angron and the World Eaters, continue to ravage each new system they come across - upon the garrison planet of Armatura, this relentless savagery may finally prove to be their undoing. Worlds will burn, Legions will clash and a primarch will fall.

Far out on the Eastern Fringe, the realm of Ultramar stands alone. Having weathered the Word Bearers' attack on Calth and the subsequent Shadow Crusade against the Five Hundred Worlds, the Ultramarines primarch Roboute Guilliman now draws all loyalist forces to Macragge as he contemplates a new future for mankind.

Perturabo - master of siegecraft and the executioner of Olympia. Long has he lived in the shadow of his more favoured primarch brothers, frustrated by the mundane and ignominious duties which regularly fall to his Legion. When Fulgrim offers him the chance to lead an expedition in search of ancient and destructive xenos weaponry, the Iron Warriors and the Emperor's Children unite and venture deep into the heart of the great star maelstrom that haunts Perturabo's dreams.

Of all the Legiones Astartes, the White Scars of Jaghatai Khan remain the most enigmatic and elusive. Born of a civilisation that prizes honour, speed and fearsome loyalty, their allegiance has yet remained unclear even as the galaxy is torn apart by Horus's treachery, and both sides have apparently counted them among their potential allies in the war to come.

From the battlefields of Phall and Isstvan, to the haunted shadows of Terra itself - the greatest war in the history of mankind rages on. While the traitor Legions continue their campaign of terror across the galaxy, preparations are made for the defence of the Imperial Palace and the final, inevitable reckoning that must yet come between Horus and the Emperor....

Since the earliest days of the Great Crusade, Sanguinius - angelic primarch of the IXth Legion - was ever among the closest and most loyal of Horus' brothers. But the Blood Angels have long kept their true nature hidden from the rest of the Imperium, and when the Warmaster hints that the key to their salvation may lie in the ruins of a conquered world, the sons of Sanguinius race to claim it.

Unaware of the wider Heresy and following the Warmaster's increasingly cryptic orders, Roboute Guilliman returns to Ultramar to muster his Legion for war against the orks massing in the Veridian system. Without warning, their supposed allies in the Word Bearers Legion launch a devastating invasion of Calth, scattering the Ultramarines fleet and slaughtering all who stand in their way. This confirms the worst scenario Guilliman can imagine - Lorgar means to settle their bitter rivalry once and for all.

In the aftermath of the Dropsite Massacre at Isstvan V, a battered and bloodied force of Iron Hands, Raven Guard and Salamanders regroups on a seemingly insignificant death world. Fending off attacks from all manner of monstrous creatures, the fractious allies find hope in the form of human refugees fleeing from the growing war and cast adrift upon the tides of the warp.

Created in the Emperor's own image, the primarchs had long thought themselves to be princes of the universe and masters of their own destiny - they led the Space Marine Legions in glorious conquest of the galaxy, and no enemy of the Imperium could stand against them. However, even amongst this legendary brotherhood, the seeds of dissent had been sown long before the treacherous Warmaster Horus declared his grand heresy.

Vulkan lies in state beneath the Fortress of Hera, and yet many of his sons still refuse to believe that he is truly dead. After a seemingly miraculous rescue by the Ultramarines, Artellus Numeon, once captain of the Pyre Guard, urges the other Salamanders on Macragge to leave Imperium Secundus and return their primarch's body to the home world of Nocturne - there to be reborn in the flames of Mount Deathfire.

Only from out of great conflict can true heroes arise. With the galaxy aflame and war on an unimaginable scale tearing the Imperium apart, champions of light and darkness venture onto countless fields of battle in service to their masters. They ask not for remembrance or reward - simply to meet their destiny head-on, and only by embracing that destiny will they come to learn what the unseen future may yet hold for them....

As the Horus Heresy divides the Imperium, Corax and his few remaining Raven Guard escape the massacre at Isstvan V. Tending to their wounds, the bloodied Space Marines endeavour to replenish their numbers and return to the fray, taking the fight to the traitor Warmaster.

The Emperor's vision of mankind ascendant lies in tatters. The Great Crusade is naught but a fading memory. The dream of Unity is no more. But with Horus's rebellion spreading to every corner of the Imperium and war engulfing new worlds and systems almost daily, there are some who now ask: were the signs there to be seen all along?

With the noble Emperor Sanguinius ruling from Macragge, Imperium Secundus stands as a lone beacon of hope even as the Warmaster's forces continue to ravage the rest of the galaxy. Roboute Guilliman, still Master of Ultramar, has convinced his brother that Terra has fallen and that the mysterious Mount Pharos on Sotha now holds the key to mankind's future.