Pluto

Introduced in Episode 7 of the first season, Pluto is a giant demon hound kept by Angela. When excited, he transforms into a young man with silver hair and small double teeth. He can breathe fire, but even in human form, he cannot speak, and his habits and actions are the same as a dog's. Finny calls him "Pluto."

He kills Lord Henry by biting him and thrusting his arm into a small hill, but after being trained by Sebastian, he is taken in by the Phantomhive household at Angela's request, becoming fond of not only Sebastian but also Angela and Ash.

In the final phase, he goes on a rampage under Ash's control, burning down Ciel's mansion and the city of London. Deciding that Pluto could not return to his former self, Ciel orders him to be killed by Baldroy, Finny, and Mey-Rin, who do so with tears.