In Harry Potter and the Deathly Hallows , Harry , Ron and Hermione leave Hogwarts to complete Dumbledore 's task : to search for and destroy Voldemort 's remaining four Horcruxes , and then find and kill the Dark Lord . In Harry Potter and the Deathly Hallows , Harry , Ron , and Hermione leave Hogwarts to complete Dumbledore 's task : to search for and destroy Voldemort 's remaining four Horcruxes , then find and kill the Dark Lord .