The House Ghosts are basically a ghost representing the House. The House Ghosts include the Fat Lady, the Grey Lady, the Fat Friar, and the Bloody Baron. Ravenclaw's House Ghost, the Grey Lady (also known as Helena Ravenclaw), had helped the famous Harry James Potter find a Horcrux that was known to be in Hogwarts. Nearly Headless Nick, or Sir Nicholas, was once attacked by a Basilisk and was Petrified, even though he was already dead. The Bloody Baron is the only being that Peeves, an insidious ghost from Slytherin, fears. The Fat Friar was recently known to sneak to see the Fat Lady to see how fat she was, feeling "rivalry," according to a Hufflepuff student.