"The mysterious Cult Mechanicus of the 31st Millenium marched to war armed with esoteric and arcane science, their hosts of battle-automata and cybernetic soldiers guided by the cold iron logic of their Tech-Priest overlords. Theirs was the technology that shaped the Imperium, and would aid in destroying it in the fires of rebellion. Presented herein are the details of the Cult Mecahnicus during the strife of the Horus Heresy, including Army List Profiles for the wide variety of the Taghmata Mechanicum, allowing players to build and field Mechanicum armies using all of the core units available. This book also includes full details of the war engines and tactics of the Titan Maniples and the Questoris Households, as well as the rules needed to represent them on the battlefield"--Back cover.