In the world of Altadas, there are no more human births. The Regime is replacing the unborn with demons, while the Resistance is trying to destroy a drug called Hope that the demons need to survive. Between these two warring factions lies Jacob, a man who profits from smuggling contraceptive amulets into the city of Blackout. He cares little about the Great Iron War, but a chance capture, and an even more accidental rescue, embroils him in a plot to starve the Regime from power. When Hope is an enemy, Jacob finds it harder than he thought to remain indifferent. When the Resistance opts to field its experimental landship, the Hopebreaker, the world may find that one victory does not win a war.

The Regime is on the hunt, forcing the Resistance to take refuge aboard the Lifemaker, an advanced submarine that houses a special cargo: a handful of women who are can give birth to human children. To evade the Regime's own submersibles, all parties must work together, but tensions are high, and not everyone on board is looking out for the greater good. As they descend into the deeps, they quickly learn that not all monsters work for the Regime.

The Resistance takes to the clouds aboard the Skyshaker, the newly-completed airship aimed at dominating the heavens, when the land far below has become a hellish place ruled by demons. General Rommond fixes his attention on the city of Blackout, the old capital of the world, controlled by the Treasury, who are themselves controlled by the ruthless Regime. The skies above that city will no longer hide in smog; fire and fury will light up the sky. That centre of the old civilised world will either shift allegiance to the Resistance, or it will burn to the ground. Yet there are always others who will resist the attempted change of power. From sky pirates and mob bankers to the feared mechanical men of the Iron Guard, Jacob and his new family of freedom fighters will face greater challenges than they have ever faced before. As bombs drop from the sky like the iron tears of gods, there are other revelations that will shake the foundations of everyone struggling to save humanity.

The Resistance has barely nursed its wounds from the recapture of Blackout, and it is now looking to another, tougher target: the massive steam-powered railway gun known as the Landquaker. They call the vast railroad the Iron Wall, and that mounted barrel is its only sentry. It does not need another. Blackout was a sitting duck, but the Landquaker is a moving target, and not only one that shoots back, but one that shoots first. The Resistance turns to old allies and new friends, from the land-loving tribes to the land-roving biker gangs. It will need every soldier it can muster. The Landquaker was designed with a singular purpose: a monstrous gun to hold back a multitude of monsters. Except this time the multitude mans that weapon, and in its hands the land is not the only thing that will quake.

Every victory is its own defeat. General Rommond's efforts to amass technological superiority over the enemy has resulted in the creation of a weapon that could destroy everything, and a faction just mad enough to use it. The Armageddon Brigade has awoken from its deep slumber, and it seeks to wake the world with it. Attracting the brightest, and most unstable, of minds, this splinter group of the Resistance has become the greatest thorn in Rommond's side. The Resistance and the Regime must unite to defeat a foe that answers to neither of them. Yet their deep divisions and long-held suspicions threaten to end the Great Iron War once and for all—by ending everything.

The Resistance races against time to complete the missile-launcher known as the Hometaker, capable of opening a gateway to the land the Regime came from, and exposing the Iron Emperor for all the evils he has done. Everything rests on the secrecy of the mission, but from day one tongues are wagging. The atmosphere is like dynamite. An overheard word could light the fuse. With no time left on the clock, General Rommond is forced to make an audacious plan: finish the construction of the Hometaker on the move, driving straight towards the enemy, who have assembled in unimaginable force. The Great Iron War is coming to an end. It's all or nothing—their world or ours.