"The pentagram is a necessary part of any demon-raising ritual. You know that, sir. Without it…" (Prologue.6)
Many of the rituals in the book draw from familiar knowledge. How many movies have seen pentagrams or similar symbols being used to raise a demon?
"Do I seem different to you?" [Simon] asked. (1.1.123)
This is a handy bit of foreshadowing, because later, Simon will look different, and not because he gets new glasses or hits the gym, but because he becomes a vampire.
[Maia] was only half surprised the next full moon when the pains started: tearing pains that ripped up and down her legs, forcing her to the ground, bending her spine the way a magician might bend a spoon. (1.2.7)
The werewolf transformation is another familiar supernatural event to anyone who has seen American Werewolf in London or Hemlock Grove.
Open, she willed the door, open, open, OPEN! A noise like ripping cloth tore through the room. Clary heard Isabelle cry out as the door blew off its hinges entirely, crashing into the cell like a drawbridge falling. (1.6.32)
This is supernatural even in the context of this series. Clary draws an unlocking rune on Jace's cell door. No big whoop. But it is a huge whoop when she literally blows the door off its hinges, and this is a hint to her superpower she'll later discover, a power to create super-strong runes.
[Jace] brushed past Clary, smelling of wet leather and char. She saw him smile as he turned, and then he stepped backward into the reflection of the moon—and vanished. (2.8.222)
Using the moon as a gateway to another world is wild and crazy even for Clary, and she's seen a lot by this point.
"The demon energies change us, make us different—you can call it a sickness or whatever you want, but the demons who created vampires and the demons who created werewolves came from species who were at war with each other." (2.12.59)
Maia blames her hatred for Simon on supernatural forces beyond her control, instead of the supernatural racism that it is.
"NAKIR!" she cried, staggering to her feet, the blade outstretched and pointed at the Raum demon. (2.12.118)
The angel blades will be familiar to anyone who read the first book. This is a rare occasion when Clary actually uses one to fight and hold her ground.
Of course, Jace though, neither the boy nor the motorcycle was really alive; they both ran on demon energies, fed by the night. (2.13.3)
The vampire might be familiar, but the demon motorcycle is a nice touch from the first book, and a unique device that reminds us we're in this magical world.
"I've never seen that Mark before," [Luke] said finally. (3.13.69)
Any supernatural story has to up the stakes at some point, and that's what Clary's mysterious new power does. She's able to create brand-new runes that surprise everyone.
How do you know you can't, said a soft voice in his head, if you've never tried it? (3.15.265)
Jace, too, ends up with a new power, one that we're not sure what its limits are.