Vestigium (pl. Vestigia) is the imprint magic leaves on physical objects or places. Someone who encounters vestigia may experience smells, tastes, sounds, and feelings related to the original event. Vestigia can be removed or transformed, as well as stored and used though exact mechanism of this process is unclear.[1][2]

Vestigia can be created by magical events such as spells or the creation of magical objects/constructions, however all living things seem to create some amount of vestigia. The intensity of vestigia relates to the intensity of the incepting event, time, and the material and/or location it occurred in.

Quantifying Vestigium Edit

The Yap Scale Edit

In order to quantify vestigium, Peter Grant created the Yap-scale based on Toby's reaction to vestigia in the area or on an object. The scale on based on the intensity of the reaction dog's reaction, specifically the number and loudness of his barks. The Yap scale is an SI-unit denoted 'mY' for milliyaps, 'Y' for yaps, and kY for Kiloyaps.

Background Vestigia Edit

Historical locations like central London or old houses have a low degree of vestigium at all times. The formal name for this phenomenon is sensis illic, but Peter Grant tends to calls it background vestigium.[3] Peter assumes approx. 200 miliyaps (200mY or 0.2Y) background vestigia which can vary in magic intense environments like the Folly.[3] Toby reactions seem to be independent of the magic's source, and reacts consistently to magical effects generated by ghosts, practitioners, vestigium, and fae.

Materials Edit

Peter Grant, with the help of Toby, examined how long different materials retains vestigia. Yap-scale

Table 1: Longevity of Vestigium among various materials as measured on the Yap Scale Edit

Material Scale Examples Citation
Stone Excellent e.g. The Hangover Stone, Café de Paris [2]
PVC Plastic Very Good e.g. Skygarden Internal Construction [2]
Concrete Very Good e.g. Skygarden [2]
Other Plastics Okay [2]
Metals Okay Toby is not sensitive enough to distinguish between metals [2]
Glass Okay [2]
Wood Poor e.g. Gate in Herefordshire [2], [4]
Flesh Very Poor e.g Cyrus Wilkinson [3], [2]

Individuals and their vestigiumEdit

Supernatural creatures, and people with magical abilities, seem to send out vestigia that reflect their personality or powers. For instance when Peter first met Mama Thames, he could smell salt water, coffee, bananas, diesel, fish guts and chocolate.[1]

When Peter met Mellissa Oswald he could hear click-clicks of legs and mandibles and feel the flicker of wings and a hot communal breath from a beehive.[4]

Lady Helena Linden-Limmer and her daughter Caroline both have a vestigium that smells of candle wax and hyacinth.[5]


  1. 1.0 1.1 Rivers of London
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Broken Homes
  3. 3.0 3.1 3.2 Moon Over Soho
  4. 4.0 4.1 Foxglove Summer
  5. The Hanging Tree