A brutal, horrifying, and magnificent story encompassing the primarch Fulgrim's journey from one of the Emperor's chosen ones to an agent of Chaos bent on assisting Horus' vision of all-out galactic war. Having read the previous four in this series, I was able to clearly place where Fulgrim fit in with the overall saga, and McNeill does a masterful job of furthering the saga while describing how elements of this novel mesh with events of the previous four. The civil war that occurs on Isstvan V between various Legions (some traitors, some loyalists where the Emperor is concerned) is nothing short of epic in scope, and the reader should easily pick up on how the galaxy will be grim and dark with war from this point on. That idea is driven home at the end, when it is revealed how the Warp's dark Chaos has infiltrated those traitorous to the Emperor, Fulgrim himself confronting Horus as one of these dark agents. This sets up well for the coming invasion of Terra.