There are things much worse than death
An original editorial by Stephanie L.
So, good old J.K. Rowling has set us a new puzzle to ponder: the question we should be asking isn't "why did Harry live?" but "why didn't Voldemort die?". This is something that personally, I hadn't considered much before she mentioned it. Clearly, something about Voldemort that is essential to his very existence prevented him from being killed with the rebounded Avada Kedavra curse, and as Harry prepares to meet him for a final battle, this mysterious quality is something he'll have to overcome in order to be victorious.
First, I would like to examine transformations. There are numerous mentions of Voldy undergoing "dangerous magical transformations," being "unrecognizable," and there not being "enough human in him left for him to die" (forgive the imprecise quotes; I don't have my books with me). Clearly, Voldemort has changed himself with Dark Magic. Is it enough to stop death? Let's look at the different kinds of transformations we've learned about so far:
1) The Polyjuice Potion: temporary, complicated to make but easy enough for a bright 12-year-old to figure out. This transformation is not something Voldy could use, as it does not seem to have life-prolonging powers.
2) Animagi: The voluntary transformation of a witch or wizard into an animal. Takes years to develop the capacity, but lasts for a lifetime (seemingly). The only way this would help Voldemort would be for him to become an immortal animal. The only known one being the Phoenix, which would seem directly opposite to his character, and it seems a wizard cannot choose the form of his Animagus.
3) Werewolves: Do not have control over their transformations; lose their mind along with their human form. Also of no use to Voldemort, as they are still mortal.
4) Metamorphmagi: We don't know much about them yet, but Tonks said you had to be born one. It's conceivable Voldemort is a metamorphmagus, but I don't see how that would prevent death.
That is all the magical transformations I can think of at the moment, forgive me if I skipped any! My point concerning them is that it's doubtful any of them are Voldemort's secret to defy death. The transformations he underwent to become Lord Voldemort are clearly of a less savory nature, that we have yet to learn of. I have three possible theories of how he did survive, however.
1) Voldemort stumbled on some ancient Dark Magic to make himself immortal.
Again, this seems doubtful. He did spend all of PS/SS trying to get the Elixir of Life, therefore he did not have a Dark one of his own. He wouldn't have needed the Philosopher's Stone if it was truly impossible for him to die. Also, this would not be very exciting from a literary standpoint as all Harry would have to do would be to find out that secret, and (knowing Harry) get Hermione to find out how to undo or break it.
2) Something about Tom Riddle was indestructible- even before he became Voldemort.
One way he could be "immortal" in his pre-Voldy days would be if he were a vampire. We know practically nothing about vampires in the Harry Potter universe. I don't have Fantastic Beasts and Where to Find Them with me either, but as far as I can recall there was no actual entry on vampires. I think there was mention of them being classified as non-humans by choice, along with centaurs and mermaids. But we do know they exist. I am no vampire buff, but I looked them up and here are some common characteristics from myth to myth:
-Vampires maintain immortality by drinking the blood of other humans to receive their strength. Sound familiar? Unicorn blood in PS/SS, then all the blood symbolism in Voldemort's rebirth and the taking of blood from Harry, to get Lily's protection.
- They hate garlic. Don't know how this could fit.
- The sight of sunlight destroys them. No, Harry will have to do more than get Voldemort out in the sun. However, he is never in a scene in the sun.
- Physical appearance tall and thin, corpse-like. Definitely could fit.
As far as textual evidence, Quirrell was said to have met vampires in the Albanian forest. Now, we know he actually met Voldemort, but wouldn't that be cool if it was Voldemort who was a vampire? One of those "oh my gosh, it was staring me in the face" kind of moments, like Harry feeling as if Snape and Dumbledore can "read his mind". There was an essay Lupin set about vampires in PoA, everyone says this is evidence that Snape is a vampire, and I could see that too. But here is clear mention of vampires as Dark creatures; Voldy would probably term them his "natural allies". Voldemort/Riddle is consistently described as pale, dark haired, thin. He is never outside in the daylight, as far as we have seen. Vampires are a big mystery. Does Avada Kedavra work on them? Could it destroy them as it does ordinary humans? We don't know but I'd bet it's more complicated than that. It could weaken them, even separate spirit from body as happened to Voldy, but it comes down to us not knowing.
This theory was one I favored until I actually began writing about it. Now I'm not so convinced, mostly thanks to intense late night HP discussions with my roommate. Voldemort seems more like a symbolic vampire, living off of other's strength at the moment. However, I do firmly believe that something inherent in Tom Riddle is essential to the destruction of Voldemort. Harry and Riddle, as we are so often reminded, are very similar. They are almost one person, and they could each have taken the path the other chose. It all comes down to their choices, and that has made all the difference. So whatever it is about Voldemort, Harry has a better chance of knowing than anyone else, hence he is "the one".
3) Voldemort bound his spirit to something either inanimate or living that survived. It even could be Harry that the spirit is bound to.
I know this one sounds very much like Sauron and the Ring in the Lord of the Rings. But it is a possibility for Voldemort, he knew enough to leave a memory behind at the age of 16. So would he have done this by accident or on purpose? He wouldn't have been planning to be destroyed, and the night at Godric's Hollow sounds like a big mess for both sides, so maybe he unintentionally left part of himself or something else in Harry as the curse rebounded. He does have the strange dream connection with Harry, and as a matter of fact dreams are consistently mentioned, though appearing innocent, throughout the series that could indeed have been influenced by Voldemort. The main problem is that now Voldemort is back, he obviously has his spirit, and Harry didn't really notice anything missing from his soul that we heard of. For more in this vein, the North Tower articles on the changeling hypothesis have some very interesting points. I think this Voldemort/Harry connection might be superfluous, however, there being enough connections between them already. The cryptic prophecy, their wands, the blood in GoF- they are really well connected.
But Voldemort might have made preparations to leave his spirit behind if he was destroyed. His "transformations" could have involved separation of body and soul, at least, at the moment of death. He could even have planned to leave his spirit with the one who destroyed him. Of course, he wasn't with Harry; he was very specifically in an Albanian forest, possessing small animals -the one power left to him. It sounds a lot like Nearly Headless Nick describes being a ghost -not wanting to pass on. Somehow, Voldemort succeeded, as he says himself, "of the steps he had taken to prevent death, something must have worked".
What that is, we can still only guess. Several possibilities exist, but I have no doubt, since JKR herself pointed it out, Voldemort's power to overcome death is extremely crucial in both the back story and Harry's coming confrontation with him. And remember Dumbledore's fight at the end of OotP? Dumbledore says "We both know there are other ways of destroying a man, Tom". He says that Voldemort's death alone would not satisfy him, and there are worse things. Voldemort's biggest fear is death, and he cannot understand this reasoning. Perhaps the way Harry will ultimately defeat Voldemort will be with a "fate worse than death," an endless twilight zone of pain that he gets trapped in, perhaps life as something like a ghost where he had no powers or influence on the people around him. Again, there are many, many possibilities. I personally think that Harry, using his capacity to love, somehow does condemn Voldemort to a half-life worse than death.