Pluto

Pluto also known as the Demon Dog is a large dog that terrorizes the town of Houndsworth until Sebastian tames him. Afterward he lives at the Phantomhive Estate. He can breathe fire walk through barriers and shapeshift into a human. As a human he retains doglike qualities. Although Sebastian hates dogs Pluto has taken a liking to him and gets jealous when he receives less attention than a cat. He only listens to Sebastian039s orders. Finnian is in charge of walking him as he is the only one strong enough to do so. Pluto appears only in the anime adaptation Source: Wikipedia