Brennan Doyle

Brennan Doyle is known as an expert in hauntings. It is later revealed that he was Dorian's childhood imaginary friend. He is an unknown creature that has been feeding on Dorian's loneliness. His existence separate from Dorian is unknown. He is a sadist that has been spending decades viciously torturing the spirit of Constance Harker.

Dorian finally defeats Brennan by destroying his painting killing himself and freeing Constance in the process. (Running Away with You)

Dorian thought that he imagined him again when he was in a psychiatric hospital. Dorian later attacked him thinking him not to be real but in fact put him into intensive care. (Ever After)