A great addition to the Horus saga, this one details the concurrent civil war on Mars raging between loyalists to the Emperor and the Horus motivated Dark Mechanicum. Adept Zeth rescues Dalia, a transcriber, from execution with the aim of using her to develop a machine that can allow mankind to reach unheard of levels of intelligence. Zeth, along with many others who make up the massive fabrication machine that Mars has evolved into for the Emperor's use, is unaware that elements exist who want to separate Mars from the Emperor's control. What follows is an exciting, well-written, slam-bang story that details the war that breaks out and the agonizing choices the sympathetic characters make as a result. I was very anxious to read this one due to how hard it was to obtain (rare book for some reason), and I wondered how the back-story of the Mechanicum figured into the galaxian wide war that the Horus series is developing into. These two major plot lines mesh together very well.