Calcifer

Calcifer is a Fire Demon in a magical contract with Wizard Howl. He was originally a falling star, whom Howl was able to catch before he fell to earth and extinguished. He is a very powerful creature himself, with a great deal of magical ability, though cannot move beyond the confines of the hearth in which Howl keeps him without the wizard's help.

He appears as a teardrop-shaped flame, blue in the books and orange-red in the movie, colored differently in different places in such a way as to make a face. He has tiny licks of flame that serve as arms and legs, though they are not very large and hardly useful.