The Bloody Baron is better known as the Slytherin ghost at Hogwarts School of Witchcraft and Wizardry. He appears throughout the entirety of the Harry Potter series, though his true name is unknown.

When the Baron was still alive, he was very much in love with Helena Ravenclaw, though she never returned his affection. When Helena stole her mother’s diadem and ran away, Rowena sent the Baron after her, knowing that he was certain to bring her back. When he did discover her in a forest in Albania, Helena refused to return with him. In a fit of rage, he stabbed her in the chest; he was then overwhelmed by so much remorse that he utilized the same weapon to kill himself.

As a ghost, the Bloody Baron is described as being grim, terrifying, and covered in silver bloodstains. In the books, he does not speak, and he wears “chains as an act of penitence” for killing Helena. The Baron is the only known being aside from Albus Dumbledore with the ability to control Peeves the Poltergeist.

In the films, the Bloody Baron is played by actor Terence Bayler from New Zealand.