After seven long years of conflict, the Horus Heresy nears its end. But now, as the Warmaster Horus marches on Terra to rip his father from the Throne, the seat of the arch-traitor’s power lies empty. Cthonia, a world once dominated by brutal murder-gangs, is occupied by the Emperor’s praetorians—the indomitable Imperial Fists. For the Sons of Horus, this outrage demands a reckoning.

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.

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.

Opal is a gleaming shrine world of saints and soldiers, beloved of the Emperor Himself. Sent to retrieve the skull of the revered Saint Veres, Sister Superior Augusta of the Order of the Bloody Rose and her squad find themselves in the midst of the capital’s holiest festival, a time of reverence and celebration. But all is not well – despite what its planetary leaders would have Augusta believe, political danger bubbles under the surface, and rebel attacks gnaw away at the city’s outskirts. The greatest threat, however, is yet to come.

Valorous Heart. Our Martyred Lady. Bloody Rose. These names of Adepta Sororitas orders are famed across the galaxy, as are the Battle Sisters who serve the emperor's will. To die in the name of the God-Emperor of Mankind is to live eternal, and none are more willing to bleed in his name than the Adepta Sororitas - the Sisters of Battle. The Book of Martyrs charts the deaths of these exemplars.

On the grim death world of Fenris, the Space Wolves Chapter selects its aspirants from the best and brightest of the young tribesmen. Ragnar of the Thunderfist tribe finds his life changed forever when he is chosen. After being revived from a savage death on the battlefield, Ragnar is recruited into the fearsome Space Wolves Chapter. He is then thrown into a galactic war against the dark forces of Chaos. However, the implanting of the Canis Helix unleashes his primal instincts and Ragnar must fight to control the beast within him.

Faced with an ork invasion of Piscina IV, the 3rd Company of the Dark Angels believes the threat to be minimal. As enemy numbers continue to increase, their commander, Captain Belial, insists that his Company are strong enough to resist. But Scout-Sergeant Naaman knows just how dangerous this foe can be, and when a renewed offensive takes the Dark Angels by surprise, the orks swarm towards Kadillus Harbour.

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.

On the prison world of Zartak, darkness has fallen on arbitrators and inmates alike. The Night Lords have come, bringing with them the shadow of fear and pain. But these monsters are not the only ones with an interest in Zartak. From the void, running on silent, another fleet emerges. These Space Marine warriors are grey-clad and white-faced, and their eyes are as black as the Outer Dark – the savage Carcharodon Astra.

On the forge world of Morod, the machines never stop and the work never ends. The population toils in the mines and factoria to protect humanity from the monsters in the void, while the Adeptus Mechanicus enjoy lives of palatial comfort. Genetor Gammat Triskellian seeks to end this stagnant corruption. When he learns of a twisted congregation operating within the shadows, one which believes that the tech-priests are keeping people from their true salvation, he sees in them an opportunity to bring down Morod's masters and reclaim the world in the name of progress.