||This article is about the Novel by Dan Abnett, for the Inquisitorial Ordo see Ordo Hereticus
Hereticus is the third and final novel in the Eisenhorn Trilogy by Dan Abnett.
Across countless worlds, the Inquisition pursues a secret war against humankind’s foulest enemies – the alien, the unclean and the unholy. When a battle with an ancient foe turns deadly, Inquisitor Eisenhorn is forced to take terrible measures to save the lives of himself and his companions. But how much can any man deal with Chaos before turning into the very thing he is sworn to destroy?