Story-world reference · opening-premise clearance
How magic is described
Start with Peter Grant’s apprenticeship in Rivers of London. The terms below are orientation points rather than a complete rulebook. The author’s opening book establishes the police-and-apprentice premise; the separate licensed tabletop game makes some procedures explicit for play. Game rules are labelled here so they do not silently become claims about the novels.
Forma
A learned magical form: the repeatable unit a practitioner practises. The language of forms helps Peter ask how an effect was produced, rather than simply naming it “magic”.
Vestigia
Sensory traces associated with magical activity. A practitioner may interpret these impressions as investigative evidence; the licensed game separately formalises sensing them as a skill.
Signare
An individual practitioner’s characteristic magical signature. The licensed game supplies a detection procedure; a game mechanic should not be read as a verbatim rule governing every novel scene.
Newtonian magic
The Folly’s systematic teaching tradition. It gives Peter a working vocabulary and a way to practise, while the stories also depict powers and traditions outside his training.
Genius loci
A spirit associated with a place or waterway. The river families are characters with relationships and interests, not a map legend for every real stream.
The demi-monde
The loose social world of people and beings touched by the supernatural. It is a community description, not a single organisation or a uniform magical species.
Practitioner
Someone who can perform magic; Peter learns within the Folly, while the wider story world includes other traditions and practitioners.
The Folly
The police unit and its workplace; the opening novel puts Peter under Nightingale’s instruction there.
River court
A social and political grouping around a river family. The first novel introduces conflict involving Thames powers; later obligations should be read in their individual book context.
Falcon incident
A police label for a possible supernatural case. The label tells you how an investigation is approached, not whether every unusual event has already been explained.
Source boundary
Author’s first-book description ↗ supports Peter’s recruitment and Nightingale’s apprenticeship. Chaosium’s licensed player crib sheets ↗ document the game vocabulary and procedures for vestigia and signare. The short interpretations above are this guide’s editorial summaries. For plot-specific applications, follow the individual books.