With the Dark Angels spread across a hundred systems, primarch Lion El'Jonson stands as Lord Protector of Ultramar - though his true motives are known to few indeed, and old rivalries on the home world threaten to tear the Legion in half. But when word comes of the Night Lords' attack on Sotha, the Lion's brutal actions bring Imperium Secundus once again to the brink of civil war.

After Isstvan, after Deliverance, the Raven Guard still endure. Their primarch Corvus Corax has rallied countless warriors to his banner, striking back at the forces of the Warmaster on every front - from the degenerate hereteks of the Mechanicum to the cruel legionaries of the Sons of Horus, none shall escape his wrath. But although Corax has managed to stall the physical corruption of his own Space Marines, what of their spirit? And what sinister end must await those who dwell forever in the darkness?

While Horus' rebellion burns across the galaxy, a very different kind of war rages beneath the Imperial Palace. The 'Ten Thousand' Custodian Guard, along with the Sisters of Silence and the Mechanicum forces of Fabricator General Kane, fight to control the nexus points of the ancient eldar webway that lie closest to Terra, infested by daemonic entities after Magnus the Red's intrusion.

From out of the shadows of the Silent War, a hero emerges. Clad all in grey, an errant warrior of the Legiones Astartes kneels before the Regent of Terra, and accepts a solemn new duty - Battle-Captain Garro, once commander of the Eisenstein, now Agentia Primus of Malcador the Sigillite. From the desolation of Isstvan to the halls of the Imperial Palace itself, he stands as a paragon of loyalty and protector of the innocent, ever ready to strike back at the traitorous allies of the Warmaster.

While loyalist and traitor forces clash on a thousand battlefields across the galaxy, a very different kind of war is being fought in the shadows - a war of subtlety and subterfuge, unknown to many, but one that surely holds the key to victory for either side. Rogal Dorn and his Legion prepare to defend the Solar System against the armies of Warmaster Horus, even as Malcador the Sigillite charges his many agents and spies with missions of the utmost secrecy. The future of the Imperium is being shaped by unseen hands....

Removed from the concerns of the galaxy at large and regarding the Warmaster's unfolding Heresy with cold detachment, he has dedicated his hollow existence to the preservation of all the knowledge once held in the great libraries of Tizca, should mankind ever seek such enlightenment again. But his sons can see the change in their primarch - he is a broken soul whose mind and memories are slipping away into the tumult of the warp.

With the noble Emperor Sanguinius ruling from Macragge, Imperium Secundus stands as a lone beacon of hope even as the Warmaster's forces continue to ravage the rest of the galaxy. Roboute Guilliman, still Master of Ultramar, has convinced his brother that Terra has fallen and that the mysterious Mount Pharos on Sotha now holds the key to mankind's future.

Driven almost to the brink of self-destruction at Isstvan V, the Iron Hands now seek vengeance for the murder of their primarch Ferrus Manus. Gathering survivors from the Raven Guard and the Salamanders aboard any vessels capable of warp travel, these Shattered Legions wage a new campaign of annihilation against the traitor forces across the galaxy - a campaign masterminded by legendary warleader Shadrak Meduson.

Imperium Secundus lies revealed as a heretical folly. Terra has not fallen, though it remains inaccessible. Sanguinius, Guilliman and the Lion El’Johnson, the primarchs of the Triumvirate, must reach Terra at all costs. They seek to defend the Emperor and to atone for their sins. But the Ruinstorm, a galaxy-wide maelstrom of chaos, hides the Throneworld from the primarchs. Now the fleets of three Legions depart Macragge, and the primarchs will stop at nothing to overcome the Ruinstorm.

As the Warmaster's campaign of galactic domination continues, his generals seek out fresh battlefields to conquer. After leaving the Crone World of Iydris behind, Perturabo strikes for Tallarn. A bitter, vengeful primarch, the lord of the Iron Warriors unleashes a deadly bombardment against the world, killing millions but entrenching the survivors. A brutal, all-consuming armoured conflict ensues, the greatest of the war and one that grinds down all combatants over more than a year of relentless battles.

Reborn in body and spirit beneath Mount Deathfire, the primarch Vulkan gathers his most trusted sons and prepares for the final part of his journey. The Legions shattered at Isstvan V have stalled the Warmaster’s advance across the galaxy, but fresh cracks are spreading through the alliance between the Iron Hands, Salamanders and Raven Guard, along with mysterious rumours of the return of Ferrus Manus. Haunted by a sense of destiny unfulfilled, Vulkan must choose between joining their war of vengeance against the traitors and following his own barely understood path all the way to the Throneworld itself.

The time has come for Leman Russ, primarch of the Space Wolves, to fulfil his vow and attempt to stop Warmaster Horus before he breaks through to the Segmentum Solar. In the face of opposition from three of his brother primarchs, Russ withdraws the Space Wolves legion from Terra and makes all haste for Horus’ position. Reports from Malcador the Sigillite’s agents suggest that Horus is utterly changed and infused with a diabolical power so great that no man can stand against him.

After a long and gruelling conflict, the traitors at last close upon Terra. But time is dwindling for an attack. Both Guilliman and the Lion are returning with all haste, and their armies could turn the tide. The hosts of the Warmaster must unite, for only then can they attack the Throneworld itself. While Mortarion is sent on ahead as the fleet’s vanguard, it falls to Lorgar and Perturabo to marshal Fulgrim and Angron, both now elevated to daemonhood and perhaps beyond even the will of the Warmaster to command.

A galaxy burns and brother turns on brother as the conflict brought about by a beloved son’s betrayal reaches its fateful end. The Warmaster Horus has triumphed. His massive fleet at last nears Terra and the patriarchal Throne of his hated father. Many have fallen to bring this moment about; their tales are the ashes upon which the Heresy was born and prospered. Others have played their own small parts, drops in an ocean of war and blood. None of it matters. Terra looks to the skies as it raises its defences. Armies muster, heroes raise their swords, citizens cower. The war is coming. And nothing can stop it.

As the darkness of the war slowly consumes the galaxy, those who still serve the Throne are faced with a struggle for their survival and the continued existence of everything they hold dear. With the threat of the Warmaster's fleet looming ever closer to Terra, it will fall to such heroes to halt the tide, but the enemies arrayed against them are powerful, and the burden of loyalty is great....