What is the name of the fire demon in 'Howl's Moving Castle'?

The fire demon in Howl's Moving Castle is Calcifer. He lives in the castle's hearth and supplies the magical power that makes the strange, walking structure move.

Calcifer is bound by a magical contract to the wizard Howl, although the exact nature of that arrangement is initially hidden from Sophie. Despite his fiery appearance and sharp tongue, Calcifer is witty, anxious, and often surprisingly cooperative. He helps Sophie operate the castle and becomes an important ally during her journey.

The film gradually reveals that Calcifer and Howl's lives are linked. Sophie is eventually able to break the contract, restoring Calcifer's freedom and helping Howl recover. The other listed characters are unrelated: the Witch of the Waste is a powerful sorceress, Turnip Head is an enchanted scarecrow, and Prince Justin belongs to the film's political storyline.