For nearly 10 millennia, the Crimson Fists waged war against the enemies of mankind from their home planet of Rynn's World. And then, in one cataclysmic event, Rynn's World fell, despoiled by the hordes of the orks. Six months later, Chapter Master Pedro Kantor leads the shattered remnants of his Space Marines in pursuit of a force of greenskins still clinging to life in the mountains of the devastated world.

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.

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 Horus Heresy is a civil war on a scale the likes of which the galaxy has never seen before. After the Great Crusade united the disparate worlds of humanity, the very warriors who made it possible turned on each other and tore it apart. The Siege of Terra looms, and the fate of the galaxy balances on a razor's edge.

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.

After the Great Crusade united the disparate worlds of humanity, the very warriors who made it possible turned on each other and tore it apart. This war was not only fought on a galactic scale – it was contested a million times over in brutal battles between former brothers and allies. Since the near-destruction of the Iron Hands, Raven Guard, and Salamanders on Isstvan V, scattered warbands from these 'Shattered Legions' have waged a guerrilla war on Horus' forces across the galaxy.

The primarchs, nigh-immortal sons of the Emperor of Mankind, take the stage in a series of short stories showcasing some of their great deeds and hideous acts from across the Great Crusade and the Horus Heresy.

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.

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.

It is the thirty-second 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. But an ork invasion of unparalleled scale throws the Imperium into disarray. As worlds burn and renowned Space Marine Chapters are destroyed, can the Imperium pull together to defeat the Beast?