I'd just finished a job in Canada, checking out a report of Black Masses being celebrated, and was on a get-well tour in New York...
The Apocalypse Door provides examples of:
- Action Girl: Sister Mary Magdalene.
- Beethoven Was an Alien Spy:
- Call Back: When Sister Mary Magdalene shows up, there's a call back to their first meeting in "Stealing God".
- Celibate Hero: Peter Crossman, being a priest, and Mary Magdalene, being a nun. (It is established, though, that Crossman wasn't celibate before he became a priest.)
- Confess in Confidence: A really twisted example.
- Cross-Melting Aura:Wherever the rosary touched the bag above the fungal glop, a thin trickle of grey smoke rose up into the still apartment air.
"Looks like that'll kill it," Simon said.
[...] It wasn't the fungus that was on fire after all. It was the rosary.
- Doing In the Wizard: Subverted. Over the course of the novel, the protagonists piece together the evidence that the "demons" they're fighting are the spearhead of an extradimensional alien invasion — but then, at the end, it's suggested that they really are demons.
- Face Stealer: The mushrooms remove and wear the face of the person they're imitating. They also apparently take part of the brain, giving them access to the person's memories.
- Fantastic Catholicism: Checks off "Fights The Supernatural" and "Is Full of Badasses".
- First-Person Smartass: Peter Crossman.
- Kill It with Fire: Turns out to be the most effective way of dealing with the threat.
- Knowledge Broker: Dalrymple.
- Meaningful Rename: "Peter Crossman" is not, as he puts it, the name he was given at Baptism. Probably this is also the case with his colleagues, and almost certainly also with Mary Magdalene.
- Nun Too Holy: Sister Mary Magdalene of the Special Action Executive of the Poor Clares, "the fun nun with the gun", never actually strays beyond the bounds of her vows, but you wouldn't think it from the way she carries on.
- Oracular Head: The Head of Baphomet.
- Public Domain Artifact: The Head of Baphomet, an idol the historical Templars were accused of heretically worshipping.
- Reformed Criminal: Implied to be common among Peter Crossman's colleagues. Crossman himself is a former Company man.
- The Spymaster
- Michael's boss, called Joey.
- Peter Crossman's boss, called Prester John, is mentioned but does not appear in person.
- Twist Ending: The way the story of Michael is ultimately tied in — not the fact that Michael is Peter Crossman before he went straight, which is obvious very quickly, but the way it ties in specifically to Crossman's current case — is such that even citing the specific trope would be a big spoiler.
- You Said You Would Let Them Go: "I told you what I'd do to you if you didn't bring him back. I never made any promises about what would happen if you did."