Moaning Myrtle
She was a Muggle-born witch who attended Hogwarts School of Witchcraft and Wizardryfrom 1940 – 1943 and was sorted into Ravenclaw house. She was killed in 1943 by Salazar Slytherin's Basilisk, under Lord Voldemort's (Tom Riddle) orders. After the incident, she became a ghost who haunted the second-floor girls' bathroom (and occasionally other bathroom facilities) at Hogwarts.