Ghosts were spiritual echoes of living people, left behind after they had passed. In Hogwarts, it was common for ghosts to dwell in the castle, as each Hogwarts house had a representative: The Fat Friar for Hufflepuff, Nearly Headless Nick for Gryffindor, The Bloody Baron for Slytherin and The Grey Lady for Ravenclaw. Other ghosts included the History of Magic professor, Cuthbert Binns, who would not be deterred by a little thing like death from teaching his class. Then there was Moaning Myrtle, a former student who haunted a girls' bathroom after dying in tragic circumstances. Although ghosts could talk to the living, they could not physically interact with the living world - but if a student were to accidentally walk through a ghost, they would experience an icy chill.