Tom Riddle's diary

The diary of Tom Riddle as a young boy, the empty journal looked harmless until Ginny Weasley unwittingly started pouring her soul onto the pages. Unbenownst to her the diary was in fact cursed, and by writing in it she was feeding the spirit of a young Lord Voldemort who had used the diary as his first Horcrux. As she succumbed to the dark magic Ginny was forced to re-open the Chamber of Secrets and release one of Hogwarts' darkest secrets. Harry managed to destroy the diary with a Basilisk fang, one of the few surefire ways to eliminate a Horcrux.