Calcifer

Calcifer is a fire demon appearing in Diana Wynne Jones's 1986 novel Howl's Moving Castle. He is described as "a thin blue face, very long and thin, with a thin blue nose" made of fire, with curly green flames for hair and eyebrows, purple for his mouth, and orange for his eyes. In the Japanese animated film adaption, he is a blob-shaped orange flame, but in the scene where Howl moves the castle, Calcifer flares up and more closely resembles his description in the book. In the sequel House of Many Ways, Calcifer is described as a blue teardrop.

Overview
It is through Calcifer's powers that Howl's castle is able to move. The fire demon will obey only Howl, though Sophie does manage to bully the demon on occasion to do her bidding, sometimes with disastrous results.

Calcifer also appears in the 2004 animated film Howl's Moving Castle (Hauru No Ugoku Shiro). He is voiced by Billy Crystal in the English version and Tatsuya Gashuin in the Japanese.

Calcifer is a fallen star who was caught by Howl. Calcifer didn't want to die, so he struck a deal with the wizard. Calcifer got Howl's heart and a prolonged life, and Howl received full access to all of Calcifer's considerable powers.

After a while, both Calcifer and Howl resent the contract, but it cannot be broken. When Sophie Hatter comes to Howl's moving castle, Calcifer recognizes that she is under a curse thanks to the Witch of Waste and that Sophie has considerable powers of her own of which she is unaware. To break his own curse, Calcifer offers to lift the curse placed on Sophie once she manages to break Calcifer's contract with Howl.

Unfortunately, neither Calcifer nor Howl could directly tell Sophie what the contract was and thus she must figure it out on her own. Sophie eventually discovers what the bargain is, uses her newfound magic to give Calcifer another thousand years of life, and to return Howl's heart. Calcifer stays with Sophie and Howl in the castle, fulfilling much of the same duties as he did before, and he is able to come and go as he pleases.

In Castle in the Air (1990), the semi-sequel to Howl's Moving Castle, Calcifer spends most of his time as a magic carpet that works best when flattered, until Howl says his name, returning him to his original state.