- Anticlimax Boss: A relatively minor villain in Xenos is shown to be an ungodly powerful psyker. Not only could he force the submission of a Chaos Space Marine, he was able to tear a cipher for the Necroteuch from the walls of the saruthi tetrascape. He forced a wall to divulge its secrets with the power of his mind. It left him largely burned out, though, too weak to stop Heldane from just shooting him.
- At the end of Hereticus, a Daemonhost that belongs to Glaw was thought to be stronger than Cherubael by dint of being less stringently bound. Cherubael was apparently strong enough that he wiped the floor with it anyway, though we don't get to see it. He does make a note about being nastier than Eisenhorn ever imagined.
- Badass Decay: Eisenhorn himself undergoes an in-universe version as he gets older. By the end he is running on fumes and sheer will.
- Informed Attribute: Eisenhorn has very little interaction with aliens despite being a member of the Ordo Xenos, and seems to have made a career of locking up heretics.
- Magnificent Bastard: Pontius Glaw and Cherubael definitely count.
- Moral Event Horizon: Every Chaos worshipper has already crossed the horizon at one point. However, a few examples stand out:
I will break every bone in your body and rape that girl by your side. And break every bone in her body. Then I will drag your jiggling carcasses down to the cathedral and burn out your agony centres while I wait for the bombardment to flatten this place
- Gorgone Locke's Cold-Blooded Torture of Eisenhorn
- Cherubael's threat to Eisenhorn and Bequin at the climax of Xenos firmly establishes him as someone utterly evil:
- Pontius Glaw trying to kill all of Eisenhorn's old friends.
- Inquisitor Osma's attack on Essene.