It is the 31st millennium. Under the benevolent leadership of the Immortal Emperor, the Imperium of Man hasstretched out across the galaxy. It is a golden age of discovery and conquest. But now, on the eve of victory, the Emperor leaves the front lines, entrusting the great crusade to his favourite son, Horus. Promoted to Warmaster, can the idealistic Horus carry out the Emperor's grand plan, or will this promotion sow the seeds of heresy amongst his brothers?

Long before the coming of the Imperium, the realm of Ultramar was ruled by Roboute Guilliman, the last Battle King of Macragge. Even after learning of his true heritage as a primarch son of the Emperor of Mankind, he strove to expand his domain as efficiently and benevolently as possible, with the XIII Legion Ultramarines as his alone to command.

The skitarii are the soldiers of the Machine God, the tireless legions of the Adeptus Mechanicus. Holy warriors, they carry the word of the Omnissiah across the galaxy, destroying impure machines and spearheading the Quest for Knowledge. A discovery of ancient technology sends a skitarii legion into battle on a forge world overrun by Chaos. When a cataclysm cuts him off from his tech-priest overseers, Stroika must rally his forces and battle both corrupt machines and Chaos Space Marines.

The shrine world of Divinatus Prime has become lost to the light of the Astronomican, and no ship can piece its veil. Only the Lord of Death himself, Blood Angels Chief Librarian Mephiston, has any hope of discerning the fate of this once pious world. After enacting a powerful blood ritual, Mephiston and an honour guard of his fellow Blood Angels reach the stricken shrine world to find it seized by religious civil war. Each faction fights for dominance of a potent artefact, the Blade Petrific, said to be wrought by the Emperor Himself.  

After a series of victories, the Imperial forces are on the back foot once more. The power of Chaos is rising, the Traitors gain ground, and all hope seems lost. Can Terra endure? 

In the centuries since his return from Commorragh, Fabius Bile has distanced himself from the affairs of friend and foe, content only to oversee the cruel evolution of his New Men. But when his creations are threatened by the monstrous haemonculi of the Thirteen Scars, the Manflayer is forced to seek out new allies and old enemies alike in an effort to preserve all that he has built. Homo Novus must survive...even if Fabius Bile must die to ensure it.   

No matter the foe, regardless of the odds, the proud warriors of the Dark Angels stubbornly refuse to accept defeat. Descendants of the First Legion, they stand foremost amongst the Chapters of the Space Marines, mankind’s mightiest defenders. None fight with more grim determination than the Dark Angels, and their renowned special companies - the Deathwing and the Ravenwing - are held in awe by allies and enemies alike. Yet behind their devotion to the Imperium lies a dark obsession.

Of all the Emperor’s sons who fell to Chaos, it is perhaps Magnus the Red whose tale is the most tragic. Sanctioned because of his desire for knowledge, chastised, judged, and shattered to his very elements – there is much for the Crimson King to feel vengeful for. Yet revenge is not the only thing that draws him to Terra alongside the Warmaster’s besieging armies. He seeks something, a fragment, the missing piece of himself that lies within the most impregnable place on the planet – the inner sanctum of the Imperial Palace.

The paths of Roboute Guilliman and his fallen brother Mortarion bring them inexorably together on Iax. Once a jewel of the Imperium, the garden world is dying as the plans of the Lord of Death to use it as a fulcrum to drag the stellar realm of Ultramar into the warp come to deadly fruition. While Guilliman attempts to prevent the destruction of his kingdom, Mortarion schemes to bring his brother low with the Godblight, a disease created in the Cauldron of Nurgle itself, made with the power to destroy a son of the Emperor. 

After seven years of bitter war, the end has come at last for the conflict known infamously as the Horus Heresy. Terra now lies within the Warmaster’s sights, the Throneworld and the seat of his father’s rule. Horus’ desire is nothing less than the death of the Emperor of Mankind and the utter subjugation of the Imperium. He has become the ascendant vessel of Chaos and amassed a terrible army with which to enact his will and vengeance. But the way to the Throne will be hard as the primarch Rogal Dorn, the Praetorian and protector of Terra, marshals the defences.