Aries, Leo and Sagittarius are the three flame cats that appear consistently throughout the series. They were once leopards and they were once the Red King's, but when the Red King turned into a tree, he made the leopards turn into cats.
Aries is the color of copper. Leo is bright orange, and Sagittarius is pale gold.
They help Charlie and his friends out a lot, and they seem to live with Mr. and Mrs. Onimous. Mr. Onimous says they do because he has a special way with animals.
They have healing, and many other magical powers. Two instances of there powers are in The Castle of Mirrors when they can break through Usher de Grey's forcefield. Also, in Charlie Bone and the Shadow they manage to heal Mr. Onimous when he was badly wounded in the hospital.