This entry into the Horus Heresy series focuses on primarch Corax and the Raven Guard and how they barely escaped from the Isstvan massacre with less than 5% of their original numbers. I was grateful that the Heresy authors finally produced a novel that really focused on the core issues of Horus betraying the Emperor and how other primarchs (Corax in this case) reacted immediately after. Especially riveting is Corax's direct interaction with the Emperor himself, and how the Emperor plants the seeds of retribution into Corax's mind. What follows is Corax's attempt to acquire the gene-tech material the Emperor used himself to create the primarchs to rebuild the Raven Guard, and the traitorous Alpha Legion infiltrating the Raven Guard to destroy any attempts at rebuilding. This novel also offers hope to fans of the Emperor and his reign on Terra in describing how Corax/Raven Guard set themselves back on the path of revenge and retribution. One of the better Heresy novels since the original Heresy trilogy....