The All Souls Trilogy establishes four types of beings including humans, and creatures: vampires, witches and daemons. An ancient covenant prohibits intermingling between the different kinds of creatures.
Many of the vampires in the story are related to Matthew Clairmont. Some are family members who descend from Matthew's vampire father, Philippe de Clermont or his vampire mother, Ysabeau de Clermont. Some are members of a secret society called the Order of Lazarus and others are members of the Congregation.
Diana Bishop is the female protagonist of the story and her family is entirely comprised of witches. Many other witches are woven throughout the story as either friends, teachers or enemies of Diana.
The daemons of the All Souls Trilogy are characterized as creative and beautiful. Many famous artists are hinted at being daemons.
Famous and infamous humans are woven into the story. The longevity of vampires has allowed Matthew Clairmont to meet some of history's most interesting people.