 The arc's focus is on Warmaster Horus, the principal antagonist, and covers about two years in the overall Heresy timeline; most of this period elapses before the rebellion begins.Following the trilogy, the narrative is not strictly sequential and is often presented in nonlinear fashion from book to book.Apart from the initial trilogy, the stories often concern events that happen earlier or later than their position in the series would suggest, or may include time periods already covered in other series titles.