The series continues to grow darker in the sixth book with the idea of one’s soul being so damaged, it would never be able to be restored. A man is drugged into loving a woman, resulting in a child (who later becomes Lord Voldemort). Prejudice against oneself when refusing to love someone because of the fear of tainting them occurs when Remus Lupin denies Nymphadora Tonks because of his werewolf status.
Harry and we as readers learn that no matter how powerful or invincible one seems, no one is immortal. The number one example of this is Dumbledore’s death. This came as a huge shock to the characters as well as the audience because Dumbledore seemed unstoppable. Not even age seemed to affect him.