The Bloody Baron (late 10th century – early 11th century) attended Hogwarts and sorted into Slytherin house. The baron's real name goes unknown. He is currently the ghost of Slytherin house.

The Baron was born into nobility, no earlier than 982.^]

At the age of eleven, the Baron became part of one of the first generations of students at Hogwarts, which, was still being run by its original Founders. He was educated in the magical arts by Salazar Slytherin for the seven years that followed.

Sometime during his education at Hogwarts the Baron met Helena Ravenclaw, daughter of Rowena Ravenclaw, whom he fell in love with, though she always rejected his advances. 

Later on in his life, Helena, after stealing a diadem belonging to her mother that increased the intelligence of the wearer, ran away to Albania. Around this same time, Rowena fell fatally ill, although legend has it that it was a broken heart, possibly caused by her daughter abandoning her. Rowena ordered the Baron to go after her, which he did, eventually finding her hiding in a forest. After he had found her, the Baron tried to compel her to return with him, but she refused, and, in a fit of rage, he killed her. Overcome with grief, he proceeded to take his own life with the same weapon he used to stab Helena

Since then, he is one of the ghosts that haunts Hogwarts School of Witchcraft and Wizardry, and the ghost of Slytherin house. Covered in Helena Ravenclaw's blood to this day, he earned himself the moniker of "Bloody Baron".