The Great Crusade is coming to an end. The Emperor has returned to Terra, and Horus remains among the stars to complete the unification of humanity. As the Imperial armies fight the final battles of the century, chronicler Solomon Foss seeks to answer one question: why Sigismund, first captain of the Imperial Fists and greatest champion of the Legions, believes that the war will not end. Having received a rare audience with the Templar lord, the answers send Foss on a fascinating journey from the time before Sigismund became a Space Marine, through his first battles and oaths, to the fierce duels between the Legions.