Malleus

Malleus raises the stakes from Xenos on every axis: the threat is bigger, the institutions less trustworthy, and Eisenhorn himself is beginning to change. The novel draws him into a conflict that involves the Ordo Malleus — the Inquisition's branch dedicated to Daemon hunting — and a conspiracy that runs closer to home than any he has faced before.

What makes Malleus work as a second book is that Abnett does not simply give the reader more of the same. Eisenhorn's methods in Xenos were orthodox; here he begins to test the limits of what is permitted, and the reader is invited to track exactly when and why he crosses each line. The compromises feel reasoned rather than arbitrary, which is precisely what makes them uncomfortable.

The daemonic elements bring the Warp closer to the surface than Xenos did, and Abnett handles the horror register carefully — unsettling rather than gratuitous, rooted in character consequence rather than spectacle. The lore of the Inquisition's internal factions (puritans vs. radicals) is woven into the plot rather than explained in exposition.

For series readers, Malleus is where the trilogy's central question takes shape: how far can a principled person go before the compromises accumulate into something unrecognisable? It is essential reading before Hereticus, and rewards going back to Xenos after finishing it.