A fire demon
is a kind of magical creature that can be found in the land of Ingary
. They are usually found, if at all, as the familiar of a powerful magic-user.
Magic-users with familiar fire demons include the Wizard Howl (whose fire demon is Calcifer) and the Witch of the Waste.
The details of where fire demons come from, and why they associate with wizards and witches, constitute a spoiler for ''Howl's Moving Castle''.