Origin
Myrtle more commonly know y her nickname “Moaning Myrtle” is a dead student who formerly attended Hogwarts School of Witchcraft and Wizardry but was killed at a young age by the Serpent of Slytherin on the order of Tom Marvolo Riddle(Lord Voldermort) because of being a muggleborn.
Life in the School
Myrtle was placed in the ravenclaw house but had trouble making friends and was often teased about her appearance thus causing her to go and hide in the girls bathroom where her body was eventually found.