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 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. 

Attached to Crusade Fleet Quintus - dubbed the Cursed Fleet by many - the Ultramarines of the Ithraca’s Vengeance are drawn to a stricken world. With millions enslaved, a malign necron technology siphons the souls of the innocent and heralds the Silent Kingdom’s expansion. The Ultramarines face an impossible decision: mount a desperate last stand to destroy the Pariah Nexus, or break away and damn the entire sector to bring word of this ancient foe’s resurgence to the only being capable of halting it - the Lord Primarch Roboute Guilliman.  

The Blood Angels Chapter of Space Marines is under threat. Having obliterated all human life in the Red Scar region of space, the largest tendril of Hivefleet Leviathan ever seen in the Imperium has converged and is making relentlessly for Baal. To face this awesome foe, Commander Dante has called upon the Successor Chapters of the ancient Ninth Legion. The Sons of Sanguinius gather in numbers not seen since the dark days of the Horus Heresy. 

The hunters have become the hunted. The Night Lords flee to the dark fringes of the Imperium to escape their relentless pursuers - the aeldari of Craftworld Ulthwé. Their flight takes them to the carrion world of Tsagualsa, where their primarch died and their Legion was broken. There, history will repeat itself as a deadly assassin stalks the shadows, and the Night Lords are drawn into a battle they are destined to lose. 

The Indomitus Crusade continues its war across the stars. The primarch Roboute Guilliman has finally broken through the orkish threat bedevilling the sectors near Fenris, and makes ready to push on his bid to stabilise the Imperium Sanctus—but old and bitter foes stand in his way. Kor Phaeron, the Dark Cardinal, threatens the previously stable core of the Segmentum Solar. Waves of rebellion instigated by his infiltrating priests suggest an imminent, large-scale invasion by the Word Bearers Legion. 

A great darkness has befallen the galaxy, and the armies of Chaos are rampant. To survive, humanity must retaliate and take back what they have lost. By the will of the reborn primarch, Roboute Guilliman, is the Indomitus Crusade launched - a military undertaking that eclipses all others in known history. From the Throneworld of Terra does the Avenging Son hurl his fleets, their mission the very salvation of mankind.

In the city of Queen Mab, nothing is quite as it seems. Pariah, spy and Inquisitorial agent Alizebeth Bequin is all of these things and yet none of them. An enigma, even to herself, she is caught between Inquisitors Gregor Eisenhorn and Gideon Ravenor, former allies now enemies who are playing a shadow game against a mysterious and deadly foe. Coveted by the archenemy, pursued by the Inquisition, Bequin becomes embroiled in a dark plot of which she knows not her role or purpose.

As the Indomitus Crusade begins, fleets of mighty warships leave Terra on a vital quest to stabilise Imperium Sanctus in the wake of the Great Rift. The returned primarch, Roboute Guilliman, leads a huge force towards the shrine world of Gathalamor, where stable warp routes will allow the flotilla to spread across the beleaguered southern half of the Imperium.

Driven on by their hatred of the False Emperor, the Night Lords stalk the shadows of the galaxy, eternally seeking revenge for the death of their primarch. Their dark quest leads them to a fractious alliance with the Red Corsairs, united only by a common enemy. Together with this piratical band of renegades, they bring their ways of destruction to the fortress-monastery of the Marines Errant.

The Night Lords were once among the most potent forces of the Imperium, Space Marines who used fear itself as their weapon. Now, cast adrift from the Emperor's light and hunted as heretics after their monstrous betrayal, the Night Lords clad themselves in symbols of death and fight the Long War, bringing pain and terror to all who worship the corpse-god of Terra. A summons from Warmaster Abaddon sends these rebels on a dangerous journey that leads inexorably to a conflict with the Emperor's chosen warriors, the Blood Angels.  

After a long and distinguished career defending the Imperium from its many enemies, Commissar Cain is enjoying a well-deserved retirement on Perlia, teaching in a schola progenium. But when a Black Crusade threatens the sector, all able-bodied citizens must rise to the defence, including Cain and his cadets. As the forces of Chaos overwhelm Perlia, can the wily commissar prove himself to be a real hero of the Imperium one last time?

On the battlefields of Aexe Cardinal, the stalwart forces of the Imperial Guard are locked in a deadly stalemate with the dark armies of Chaos. Colonel-Commissar Ibram Gaunt and his regiment, the Tanith First and Only, are thrown headlong into the living hell of trench warfare, where death by an unseen enemy is always just a moment away. The only chance for Gaunt and his lightly armed scouts to survive is to volunteer for a mission so dangerous that no one else dares accept it.

In the mysterious city of Queen Mab, the forces of light and darkness are locked in a murderous struggle for truth. The dedicated agents of the Holy Inquisition battle with their shadowy counterparts, the infamous Cognitae, to discover the encrypted identity of the enigmatic, all-powerful King in Yellow. Caught at the heart of this struggle is the pariah Alizebeth Bequin. Bequin must withstand an onslaught of angels, daemons, and even the monstrous warriors of the Traitor Legions, to unpick the greatest riddle of her life. 

As Guilliman, Regent of Terra, heads off to lead the Indomitus Crusade, he leaves behind a world still in turmoil, beset by cult activity. Stripped of its huge armies for the galactic offensive, recovery is precarious. The Custodians do what they can while keeping the Palace secure, and the Sisters of Silence rebuild their citadel on Luna. When the warship Phalanx returns, it seems that stability will at last be assured. However, as reconquest forces push out further into the slums, they come across signs that another mysterious foe is active.