* The Skinless Boy.
* The worms under the Incomparable Gardens are pretty bad.
* The two clockwork figurines that rip out their prisoner's eyes. And they have no qualm about going out and getting a different pair if they can't find the one they want. It used to be vultures that went for the liver.
* [[spoiler: The Architect. That's right everyone, your god's master plan is to kill you all, and the only things preventing her from doing it are a bunch of selfish, immoral jerkasses who don't care that you exist.]]
* Most Nithlings are quite horrifying in their own right, but special mention goes to that bizarre cricket ''thing'' in Grim Tuesday as well as [[spoiler: the massive hordes Leaf has to fight off as the temporary Lieutenant Keeper.]]
* Drowned Wednesday's first meeting with Arthur. The entire affair is just so gruesomely described for a children's book that it adds an extra layer of disgust to the sheer horror of the basic imagery.