Belisarius Cawl, Archmagos Dominus of the Adeptus Mechanicus, is the most brilliant mind in the world. For ten thousand years he worked for the good of humanity under the auspices of the Emperor and Lord Commander Roboute Guilliman to stop the inevitable coming of strangers and traitors. Many call him a heretic, but everyone must recognize the greatness of his achievements, for who, if not him, was tasked with creating a new generation of Space Marines? Who else but the great Belisarius Cawl could accomplish such a task? Now, with the opening of the Great Rift and the launch of the Indomitus Crusade, his ambitions lead him to the long-dead world of Sotha, formerly home to the Scythes of the Emperor, now a barren wasteland gnawed by the vile Tyranids. Accompanied by Tetrarch Felix and his chosen warriors, Cole believes that this is where the cornerstone of his mysterious Great Work lies. But finding him is an almost impossible task, since the archmagos will have to defeat an ancient evil that threatens to extinguish the last hope of humanity.