Paper Contained within this 128-page hardback book you will find a comprehensive history of the rift that tore the Mechanicum apart, detailing the corrupt technologies employed by the Dark Mechanicum, as they came to be known. You'll learn of the Doom of Magma City, the largest conflict of this internecine war, and the forces that took part. Also included are rules for both the loyal Mechanicum, and the traitorous Dark Mechanicum, plus their Formations, and Detachments. This supplement book presents a full campaign system for linking Legions Imperialis battles together, including an Escalation Campaign that sees the forces ramping up to a final apocalyptic battle. You'll also find rules for three Formations of Legend, with their own unique special rules, plus army lists for Collegia Titanica and Questoris Familia forces. During the Age of Darkness, the Mechanicum of Mars split in two, just as the Astartes did. Fueled by righteous fury on both sides, they tore into each other with the most devastating weaponry unleashed during those bleak times, holding nothing back.