While the usage of magic varies greatly depending on the nature of the caster, some principles of magic seem to be universal.
Black magic
Black magic, according to Nightingales definition, is the use of magic in a way as to cause a breach of the Queen`s Peace.[1]
Glamour
Glamour is a way for magical creatures to make others do what they want.[2]
Obligation
When you take part in food or drink at the home of a person with magical powers, you might be put under obligation to that person.[3]
Signare
Signare is the individual signature of individual practitioner's spells.[4]
Spells
Different countries and regions have different traditions and spells.
Vestigium
Vestigia is described as an afterimage, and can manifest as feelings, smells, tastes and sounds. Intense vestigia can be created by magic, but all living things seem to create some amount of it.[5][6]
Peter Grant developed the term yap-scale, to measure how strong the vestigia is (referring to how much Toby yaps in its presence).[7]