But with the challenges, there was also excitement. (They tend to be entwined. That’s one of the joys of this game.) When I sat down with Laurie Goulding to talk about the book, and I learned what the goal of this story was, yeah, I was plenty excited. If there was to be a turning point, then the events should be big, and I wanted everything to be on a suitably gigantic scale. As I believe I’ve mentioned before, one of the things I love about writing Horus Heresy and Warhammer 40,000 fiction is its commitment to the operatic, the monumental, the grandiose. The goal I set myself, then, was to come up with set pieces that would embody these principles, while also working within the theme of the novel.

And that theme presented itself almost immediately. In order to reach Terra, the primarchs would have to defeat the Ruinstorm. And Sanguinius was going to be tempted again, this time where Horus fell. It seemed to me, then, that the Ruinstorm should be a metaphor just as much as it was a literal obstacle. I saw the tale as being about multiple temptations. Each primarch would face his own Ruinstorm. Sanguinius had triumphed over temptation once already, in Fear to Tread, but I believe it is fitting that he undergoes a second trial. The Angel’s two temptations thus mirror the two curses of the Blood Angels, one that already almost destroyed them, and one lying in wait to blight their times ahead. If the physical scale of Madail’s works (or, to be more precise, the things his passage has brought into being) is so huge, then the more insidious aspects of his plan should also be potentially catastrophic on a similar scale. Therefore, Guilliman and the Lion should also be tempted to the edge of damnation. My idea here was to show not just how powerful the Ruinous Powers are, but also to underscore the tragedy of the fall of Horus and the rest.