Red/Blue Magic

Magnus's normal magic is blue, which is a color typically associated with calm, and Alec finds it soothing once Magnus's magic returns to being blue. One Magnus is struck by Sammael's magic weapon, his magic becomes red, which is typically associated with danger.

The Jump in Diyu

The group winds up on a staircase in an impossible situation, and decide that jumping is their only option. The fact that everyone follows Magnus with the hope that he will save them is a symbol of their trust, which is unusual between Shadowhunters and Downworlders.

Warlock Marks

These are identifying features that symbolize that character's identity as a warlock. Max's mark is that he is blue and will likely grow horns. Shinyun's mark is that her face is completely expressionless.

The Black and White Swords

As is typical, there is symbolism in the colors black and...