Ghosts

Like any good magic castle, Hogwarts is highly haunted. Each house has its own ghost, with different features and personalities. Slytherin has the Bloody Baron (who is covered in silver bloodstains), Hufflepuff has the Fat Friar, Ravenclaw the Grey Lady, and Gryffindor Nearly Headless Nick. The most useful of Hogwarts’ ghosts is Professor Binns, the school’s History of Magic teacher. One day, he simply fell asleep in front of the fire in the teacher’s quarters, then got up to teach his class the next day, leaving his body behind. He may or may not realize that he’s dead, and enters his lessons through the blackboard.