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.

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?

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? 

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.  

Lord of Chemos and bearer of the Palatine Aquila, Fulgrim, primarch of the Emperor’s Children, is determined to take his rightful place in the Great Crusade, whatever the cost. A swordsman without equal, the Phoenician has long studied the art of war and grows impatient to put his skills and those of his loyal followers to a true test. Now, accompanied by only seven of his finest warriors, he seeks to bring a rebellious world into compliance, by any means necessary. 

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.

Legends abound of the glorious - or infamous - deeds of the emperor's sons. Yet almost nothing is known of Alpharius, the most mysterious of them all, for the lord of the Alpha Legion is unparalleled in the art of obfuscation. Such are his gifts of secrecy and deceit that even his rediscovery has remained an enigma - until now. But when the tale comes from the serpent’s mouth, where do the lies end and the truth begin?

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. 

In the void and upon the worlds of Greater Ultramar, the battle for the Imperium continues. Intent on rebuilding his home realm and using it as a base to reconstruct the ravaged stellar empire of mankind, the returned primarch, Roboute Guilliman, proceeds with his war to drive Mortarion and his Death Guard Traitor Legion from the domain of the Ultramarines. But when Guilliman brings his brother to battle upon the diseased plains of Parmenio, the intervention of a greater power in their fraternal struggle threatens to upend the Imperial Regent’s understanding of the galaxy. 

The primarch Roboute Guilliman of the Ultramarines has returned in the galaxy’s hour of need, and all muster to his Indomitus Crusade to hold back the darkness. Amongst these heroes is Cato Sicarius, Master of the Watch and vaunted captain of Second Company. Disaster befalls Sicarius and his brave warriors as their ship, the Emperor’s Will, is lost to the hellish warp, its entire crew believed slain. But Sicarius endures, though he and his men are fighting for their very survival against the denizens of the Great Rift - the daemons and renegades of Chaos.  

Ahriman is thrust into a deadly conflict with a creature of darkness whose cunning and thirst for power are the equal of his own - the first daemon prince, the dreaded Be'lakor.

Constantin Valdor. It is a name that brings forth images of heroism, honour and peerless duty. For it is he who commands the will of the Legio Custodes that most esteemed and dedicated cadre of elite warriors. He is the Emperor’s sword, His shield, His banner and he knows no equal. Clad in shining auramite, his fist clenched around the haft of his Guardian Spear, he is the bulwark against all enemies of the throne, within or without. Nearing the end of the wars of Unity, Valdor’s courage and purpose is put to the test as never before. 

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.

It is the 32nd millennium, and the Imperium is at peace. The Traitor Legions of Chaos are but a distant memory, and the many alien races that have long plagued mankind are held in check by the Space Marines. When a mission to exterminate one such xenos breed on the world of Ardamantua draws in more of their forces, the Imperial Fists abandon the walls of Terra for the first time in more than a thousand years.