Voldemort intended the object to be used by his most loyal follower in the event that his horcruxes were destroyed, but it ended up in Hermione’s possession instead.
It sent her back to a time when he was much less the monster that she’d always known him to be. Nothing could have prepared her for the intelligence and charm of Tom Riddle.
He isn’t who she thought he was.
Hermione discovers that it’s a dark descent into the madness of the man she should hate, but can’t… a descent she will never emerge from.