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.

For Ianthe, war is all too familiar. A former soldier in the Astra Militarum, she now serves Inquisitor Covenant as an agent of the Throne. Her first mission sees her investigating a cult called the Children of Eternity. Falling foul of the local Enforcers, Ianthe soon learns that war in the shadows is seldom straightforward and that the local, angry law-keepers are the least of her troubles.

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.

Fell times have come to the galaxy. Cadia has fallen, destroyed by the onslaught of Chaos. A Great Rift in the warp has opened, and from its depths spew daemons and the horrors of Old Night. But all hope is not lost… A hero, long absent, has returned, and with him comes the wrath of the Ultramarines reborn. Roboute Guilliman has arisen to lead the Imperium out of darkness on a crusade the likes of which has not been seen since the fabled days of the Emperor. But never before have the forces of Ruin amassed in such numbers, and nowhere is safe from despoliation.

The Custodian Guard have stood watch over the Emperor's Palace on Terra since the foundation of the Imperium. Charged with protecting the Master of Mankind from all threats, within and without, their fearsome resolve is renowned throughout the galaxy, and their golden armour is the last thing that a would-be assassin or saboteur will ever see.

In the hellish sprawl of Imperial Terra, Ordo Hereticus Inquisitor Erasmus Crowl serves as a stalwart protector, for even the Throneworld is not immune to the predations of its enemies. In the course of his duty, Crowl becomes embroiled in a dark conspiracy, one that leads all the way to the halls of the Imperial Palace. As he plunges deeper into the shadowy underbelly of the many palace districts, his investigation attracts the attention of hidden forces, and soon he and his acolyte Spinoza are being hunted.

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.

Throughout the tortured galaxy, Ephrael Stern is known by many names. The Thrice-born. The Daemonifuge. The Heretic Saint. Trapped deep within Imperium Nihilus following the coming of the Great Rift, the maligned Sister of Battle fears the Imperium is no more. The God-Emperor’s light, which has guided her through centuries of strife, has too extinguished. Seemingly forsaken, Stern is bereft until a mysterious stranger arrives, offering her a new destiny. One that might yet see the Imperium saved. Stern must prove herself worthy of the God-Emperor’s grace once more.

The feral warrior-kings of Fenris, the Space Wolves are the sons of Leman Russ. Savage heroes, few can match their ferocity in battle. After half a century apart, Space Wolves Ingvar and Gunnlaugr are reunited. Sent to defend an important shrine world from the plague-ridden Death Guard, the Grey Hunters clash with the pious Sisters of Battle—who see the Space Wolves as little better than the enemy they fight. As enemies close in around them and treachery is revealed, Gunnlaugr and his warriors must hold the defenders together.

Uriel Ventris, newly ascended to the ranks of the Primaris, leads warriors of the Fourth Company from the Indomitus Crusade of Roboute Guilliman to a world on the frontiers of Ultramar. Once a battleground against the orks, Sycorax is now under furious assault from an enemy of ancient times – the necrons. The Ultramarines have faced these baleful xenos before, but Uriel senses the hand of a foe from his past at work on Sycorax, a tally unfinished and a debt to the Imperium finally come due.

Belisarius Cawl, Archmagos Dominus of the Adeptus Mechanicus, is the most brilliant mind alive. For 10,000 years he has furthered the cause of mankind, working under the aegis of the Emperor and Lord Commander Roboute Guilliman to prevent the inexorable march of the alien and the traitor. Many call him heretic, but all must recognise the magnitude of his achievements, for who else but he was entrusted to create a new generation of Space Marines?

The fortress world of Regium has a proud history, For millennia, it has endured when others have fallen to ruin and damnation, standing defiant in defence of the Imperium of Man. But now it is shaken. Parasitic plagues run rampant, and Regium's citizens are haunted by dreams of horrific monsters feasting upon their flesh and marrow. Lieutenant Castamon of the Ultramarines recognises these signs of an impending Tyranid invasion all too well. Rallying his warriors, the battle-hardened veteran launches a strike force to slaughter the xenos in the outer system, before it can reach Regium.

In the aftermath of battle, Flesh Tearers Chapter Master Amit picks his way across the blasted landscape and is drawn into single combat with a survivor of the enemy force, a berserker dedicated to the Blood God. As they fight, Amit begins to realise that at slaughter's end, he and the servant of Khorne are not so dissimilar.

Supreme Grand Master Azrael summons Lazarus and his Fifth Company to honour an old debt on the Knight world of Reis – a planet upon which the warp has set its hungry gaze. But Lazarus is not so sure Reis wants to be saved – its Knights are long lost, its governance is dogged by political strife, and internecine conflict hampers the world’s defence against an ancient evil. ­An evil which, like Lazarus himself, refuses to die.