"Harry Potter and the chamber of secrets"

The Chamber of secrets was build by the founder of Slytherin house, Salazar Slytherin one of the four founder of Hogwarts want to banish mud blood from the school but the 3 founders don't want, so Salazar Slytherin build a chamber that secretly teach the student of Slytherin houseto practice magic without getting caught. It said to be the home of the monster which Tom Marvalo Riddle a.k.a Lord Voldemort kept inside for many of years until Salazar Slytherin "true air"(descendant)  come back to the school and spread terror to the student of Hogwarts.

Tom Marvalo Riddle- he is the past version of Lord Voldemort his spirit lived in his diary known as "Tom Riddle's Diary" one of the 7 hocruxes. He is the son of a witch moder Merope Gaunt and a muggle father Tom Riddle Sr.