Symbolism, Imagery, Allegory
Triskaideka-What Now?
In our world, there's a superstition surrounding the number thirteen. Many buildings don't even have a thirteenth floor. Tom describes thirteen as "the worst and unluckiest of all numbers" (4.7), and he might just have a point.
The number thirteen manifests itself in a few different ways throughout the book. It's the age Tom almost is. It's the number of the haunted house on Watery Lane where the Spook used to live. It's the number of years Mother Malkin has been in the pit and the number of bars holding her in.
These multiple references to thirteen are a great way to tie the magic in Revenge of the Witch with real-life superstitions. Hmm, maybe triskaidekaphobes have a point...