During the Horus Heresy, vast regions of Mars broke away from Imperial control, with the relentless production of machines and weapons from its factories becoming an increasing danger to the throneworld as the Warmaster advanced. Loyalist forces made several attempts to reclaim the planet, even as the Tech-priests engaged in internal conflicts. These events set the stage for the upcoming Warhammer: The Horus Heresy supplement, Campaigns of The Age of Darkness: The Martian Civil War. This 168-page hardcover offers an extensive collection of background details covering the entirety of this unique conflict, along with rules to bring it to life on your tabletop. It includes new core missions, apex missions, relic hunt missions, and an Onslaught campaign to integrate them into your games. You'll also find additional units, Techno-heresy rules that allow you to shape the fate of the Red Planet, and extra content from previously released Exemplary Battles in the Age of Darkness.