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Voldemort's Horcruxes: Who, When, How, and Why

In this essay it is my intention to tie up the loose ends relating to the creation of Voldemort's Horcruxes. There are quite a few such loose ends, and although none are glaringly evident, they become hard to ignore once they are discovered.

The subject of the Horcruxes is complicated, and entails a number of sources that contradict each other, either seemingly or definitely. There are also some established fan theories that, with all this information, have been shown to be misconceptions. First, we have Albus Dumbledore's account of the matter in Half-Blood Prince. Second is the established timeline for Tom Riddle's school career, in particular his fifth, sixth, and seventh years. Third we have the canonical events of Deathly Hallows. And finally, we have the recent Bloomsbury webchat with J. K. Rowling in which she reveals who the murders were for each of the six intentional Horcruxes. If you're not familiar with that chat, then here is what she said on that subject.

  • Diary: Moaning Myrtle
  • Ring: Tom Riddle Sr.
  • Locket: A Muggle tramp
  • Cup: Hepzibah Smith
  • Diadem: An Albanian peasant
  • Nagini: Bertha Jorkins

Well, I don't know about you, but the first thing that I noticed was that Dumbledore's HBP account that he gave to Harry was wrong on two counts.

One, he told Harry that he thought Nagini's murder had been the Muggle Frank Bryce.  I suspect that, in the context of the story, this is a simple mistake by Dumbledore.  (In the real-world context, it may indicate that Mrs. Rowling changed her mind about the victim of this murder.  Or it may not.)  The second contradiction with Dumbledore's account is when he told Harry that he thought Voldemort used significant killings to create his Horcruxes.  Well, some of these are significant.  Myrtle is significant as Tom's first murder.  His father is significant for the obvious reason that he hated his father.  Hepzibah Smith is significant as the person who had his family locket, and for marking the end of his tenure at Borgin & Burkes, after which we know that he began gathering followers in earnest, and never went by the name Tom Riddle again.  Bertha Jorkins is significant because she is the first person that Voldemort killed after he obtained his infant-like body, and she unwittingly provided him with critical information that enabled him to stage his full comeback.

But the other two murders, of anonymous Muggles, are not "significant" in the sense of having any "emotional" importance to Voldemort.  They were simply innocent people who happened to be in the wrong place at the wrong time.  (Although, frankly, I'm surprised that Tom didn't kill Caractacus Burke for the locket's murder, since Burke cheated his mother over that very item. I guess JKR had to keep Burke alive for him to talk to Albus, as is shown in HBP.)  But the fact that Voldemort did this tells us something very important about Horcrux creation, which has profound implications for the timeline:  It appears that they were killed for the sole purpose of allowing Voldemort to make Horcruxes, which indicates that the creation of the Horcrux must take place immediately (or very soon) after the murder itself.  A Horcrux apparently cannot be made from a murder committed at some distance in the past, or Voldemort would have had at least two other suitable soul-splits to use for these two items:  his Riddle grandparents.

The implications, as I said, are profound.

Deconstructing the Diary

Myrtle died in 1943, when Tom was a fifth year.  Although he did not use a curse against her, he clearly intentionally set the Basilisk on her, or it wouldn't have read as murder and wouldn't have split his soul.  Based on Severus Snape's memories in Deathly Hallows, apparently one can cast even Avada Kedavra on a human being, with full intent to take their life, and it only reads as murder and only splits their soul if the caster took the victim's life against their wishes.  It is heavily implied, when Dumbledore says that Snape would merely be "help[ing] an old man avoid pain and humiliation," that casting AK at Dumbledore didn't do any damage at all to Snape's soul.  The question now becomes, why Myrtle?  Was she merely a convenient "Mudblood" for Tom Riddle, who happened -- like the unfortunate Muggles he later killed—to be in the wrong place at the wrong time?  Or had she given Riddle trouble, and was targeted?  Given Myrtle's whiny, obnoxious, tattling personality, it's not out of the question that she had embarrassed Riddle, or perhaps even caught him at something (although clearly not the Chamber of Secrets, or she would have known exactly who set the Basilisk on her).  This is highly speculative, but since J. K. Rowling has revealed that Myrtle was a Ravenclaw, and since Tom definitely knew precisely how to make a Horcrux by the end of his fifth year, it could be that Myrtle had caught him in the library reading illicit material (perhaps Secrets of the Darkest Art) and threatened to tell on him.  I imagine that Tom started reading Dark Arts materials as soon as he could get his greedy hands on them, and the year that he became a prefect is a very good candidate for that time.

In any case, since it seems that Horcruxes must be made right after the murder, we can date the Diary as having been created in Spring 1943.  Tom was indeed 16 at this time, which jibes with what the Riddle spirit said in book two about its age.  The book was, at the time, the most important possession he owned, so it was the most natural object for him to use.

The Diary fragment knew all about Tom Riddle Senior, knew that he was a Muggle who had left his mother, and knew why.  On the surface, it seems that it shouldn't.  It is all but impossible for the Diary to have been created after Tom killed the Riddles, or how could it have been definite that Myrtle was the death used?  But in fact, that does not disturb me and does not present a contradiction.  Horcruxes are interactive, provided that there is enough soul fragment there to be able to interact.  The soul there is not "dead"; it can learn things.  The Locket fragment was able to pick up on Ron Weasley's thoughts and fears just by its housing being worn by him sporadically.  And the Diary remained in Voldemort's possession until 1981.  It learned the ugly history from its maker.

He probably did make the Diary as a weapon, rather than simply realizing years later that it had that capability.  And, since we know from Deathly Hallows that it would have to be destroyed by extremely dangerous and rare means, Dumbledore's statement in HBP that he was "run[ning] the risk that someone would destroy it" is put in a different light.  The risk to the book was actually not that high at all, weapon notwithstanding.  Most people would attempt to get rid of it by throwing it away, setting (normal) fire to it, or blasting it apart, which according to Secrets of the Darkest Art via Hermione, wouldn't keep the Horcrux from repairing itself.  Unless they knew it was a Horcrux, it wouldn't occur to people to use Fiendfyre or Basilisk venom unless they were already in the presence of such things, and if they were actually close enough to the Basilisk to get its venom, their chances of survival weren't that great.  And finally, the book was always intended to be deposited in the Chamber of Secrets, an area that only a Parselmouth (or one who had heard a Parselmouth speak and memorized what they said) could get into.  As far as 16-year-old Riddle was concerned, and as far as Voldemort was concerned when he gave the diary to Lucius Malfoy, that meant him and him alone.

The Ring

Moving on to the Ring:  Since we know that he used his father's death, and we know that Horcruxes must be made soon after the killing, this is all but proof that Riddle had two Horcruxes by his sixth year.  It also suggests that he probably killed his grandparents first.  Since he killed three people nearly at the same time, in order to be sure that it was his father's murder that was actually used, he probably had to kill his father last so that the Horcrux would be made from the most recent split.  And, given that he didn't even know of the Ring's existence until his uncle Morfin showed it to him, he apparently didn't go to Little Hangleton with the intention of making a Horcrux.  I suspect, in fact, that he wasn't even aware that his father was alive until Morfin let it slip.  He sounded very surprised to hear "Riddle came back."  Once he learned this, and saw the Ring, the idea came to his head.  Morfin's memory went blank after that, indicating that Tom had knocked him out with a spell and taken the Ring.  He implanted a false memory into Morfin's head as well, and used Morfin's wand to kill—but certainly not to do the memory tampering or to make a Horcrux. His own wand did that.

One last point to make about the Ring.  If Riddle made it a Horcrux in the summer of 1943, and all indications are that he did, then Dumbledore was wrong about Riddle not wearing it after he had done this to it.  He was wearing it the following term, either autumn of 1943 or spring of 1944, when he had his infamous chat with Horace Slughorn.  Now, why would he have asked Slughorn anything about Horcruxes, including whether it was possible to make several, if he already had two?  Well, I think that Riddle had a new idea occur to him on the night that he created his second Horcrux.  Before he knocked out Morfin, he heard his uncle screaming, "Where's Slytherin's locket?"

A New Idea

Going into his sixth year, Tom Riddle had a three-part soul:  his diary, his ring, and himself.  Like seven, three is also a highly important and significant magical number, but seven is apparently "the most powerfully magical number."  I think that after Riddle learned that Salazar Slytherin had owned a locket and his own mother had sold it, he came up with the idea of collecting four objects, one from each Founder of Hogwarts, and creating four more Horcruxes, to give him this "powerfully magical" seven-part soul.  What he thought this would accomplish, I have no idea; it seems that a smarter thing to do would have been to hide the Ring somewhere under the Fidelius Charm with himself as Secret-Keeper, so that no one else could ever see it.  Of course, that would have been "game, set, match," unless Voldemort could inadvertently share the secret with Harry Potter by the accidental Horcrux that was implanted within Harry.  --And assuming that such a thing would have been created in the first place with "only" two other divisions of his soul.

In any case, before Tom did this to himself four more times, he needed to get a second opinion on it.  Secrets of the Darkest Art, if Hermione and Harry are correct about that book being Tom's source of instruction, would have warned him about making one, and spoke of the instability and danger that the process caused.  So he went to Slughorn, all but gave himself away, but received nothing to suggest that creating four more would cause harm to him beyond that which was inherent to the spell itself.

It would have been around this time that he started tracking down relics from the Founders:

  • He knew that his mother had sold Slytherin's locket in London, and a bit of research (or racking his own memories, if—as I strongly suspect—he was familiar with Diagon and Knockturn Alley) would have turned up Borgin and Burkes as the most likely place for her to have sold it.  I think at this point, he made plans to go to work there in order to track down the locket.
  • As we now know from Deathly Hallows, he wheedled the location of Ravenclaw's diadem out of the Grey Lady while still a student and probably made plans to go to Albania whenever he had the opportunity.
  • We have no indication about whether Hufflepuff's cup was well-known.  As a family heirloom, it may not have been.  The owners of the Slytherin locket seem to have been unknown to the general population, at least until Merope sold it.  Then again, the Smiths were certainly more involved with Wizarding society than the Gaunts, and there may have been a record to indicate that the Cup remained in the family.  If so, Riddle would undoubtedly have found it, giving him another incentive to work for Borgin and Burkes.
  • Gryffindor's sword is linked with the Sorting Hat, which can "teleport" it into the school from wherever it is currently located, provided that a Gryffindor puts on the Hat and calls for help in a time of crisis.  I would imagine that a story of this nature circulated among the Gryffindors just as the story of the Chamber of Secrets and Ravenclaw’s lost diadem circulated among those students. Just because Harry was about as incurious as George W. Bush does not mean that everyone else was. And Tom Riddle definitely wasn’t incurious.

The Locket and Cup

In any case, as we know, he went to work at the shop, discovered the Locket and Cup in the possession of Hepzibah Smith, killed her, and took them.  This would have been some time in the late 1940s.  Rowling's murder list indicates that Smith was the death for the Cup and a Muggle tramp was the death for the Locket.  All this time, I thought that Slytherin's locket was Horcrux 3 and Hufflepuff's cup was number 4.  The order of the destruction of the Horcruxes would then mirror the order in which they were created.  A relic of Slytherin would also be of more personal importance to Voldemort than a relic of Hufflepuff.  And finally, Ron and Hermione didn't report any trouble from the Cup when they destroyed it (in contrast with the Diary, Ring, and Locket).  The Diary had put up the biggest fight, followed by the cursed Ring, then the self-aware Locket.  The Diadem went out with only a vibration and a faint hiss, Harry didn't experience protests from the soul fragment within him when he was walking to what he thought was his death, and Nagini didn't defend herself at all.  Since the soul fragments in the last three didn't fight their destruction, but the first three did, it seemed logical that the Cup was created after the Locket, and that it and the three Horcruxes made after it contained so little soul that they couldn't adequately defend themselves.

However, with the Locket being made from the death of an anonymous Muggle and the Cup being made from Mrs. Smith—yet both being stolen from her on the night she was killed—it seems to suggest that the Cup may have been #3 and the Locket was #4.  For the reasons I stated—symmetry, emotional importance, and the reported behavior of each Horcrux—I do not like this interpretation.  It's still possible for the original theory to be right, though.  Consider this timeline.

  1. Tom makes his plans to steal the two items.  En route to the Smith house, he kills a Muggle tramp.
  2. He arrives at the house, breaks in (probably by an Imperius Curse to the house-elf, who would have answered the door if her mistress was getting ready for bed), and finds the objects before anyone notices.  (Dumbledore said that the poisoning was done to her evening cocoa, so he would have had cover of darkness as well as the likelihood that she was settling down for the night.)  He makes the Locket into a Horcrux on the spot.
  3. If he has not already done so, he puts Hokey the house-elf under Imperius and makes her poison her mistress.  Alternatively, he does the deed himself and implants a false memory in the elf's mind. He may even have given her poison in the drink to make it look like that was her cause of death but used the Killing Curse (which leaves no marks) before the poison killed her. Wizards, it would seem, have no concept of forensic examination other than Prior Incantato.
  4. He leaves the house with the Cup and Locket, either before or after making the Cup into a Horcrux.

I’ve a slight tangent to insert here, but this is really the only logical place for it. When Regulus Black found out about the Locket, he did something that seems very peculiar at first: He stuck a note in his replacement. It seems vanishingly unlikely that Voldemort would ever have read the note! Only after he found out that another Horcrux had been stolen did he bother to check on the remaining ones and discover that they had been taken too. What could Regulus have meant by it?

I think we have an answer, though we must make it a theorized answer, as the canon support is only a hint. In the sixth book, Harry asks Dumbledore if Voldemort can feel it when a Horcrux is destroyed. Dumbledore says that this is a “very interesting question” and that he “believes” not. This is a strange answer to give; Horcruxes have been around since the time of ancient Greece (obviously called something different, though; that is a Latin-based term) and Dumbledore himself had at least one book that told all about them. It should not be a matter of speculation as to whether a Dark wizard could feel it when a Horcrux was destroyed; it should be a known fact either way.

I think that, though Dumbledore doesn’t come out and say it, Dark wizards usually can feel it. In fact, I think it’s probably fair to say that the only known one that hasn’t felt it is Voldemort himself, and the reason for it is contained in Dumbledore’s answer to Harry: that he had so mutilated his soul that he could not feel. The fact that Voldemort didn’t know his Diary had been destroyed was what made Dumbledore suspect this. But Regulus Black would not have assumed that his Dark Lord would have multiple Horcruxes. He would have assumed that, once Kreacher had managed to destroy the thing, Voldemort would have known it at once and would have come to the Cave to see what was to be found, thereby discovering the note he had left behind. He would also have assumed that Voldemort would have heeded the wisdom in Dark Arts books that discuss the matter, and avoided further mutilating his soul upon the discovery.

Timing a Trip

For some reason—most likely because Harry speculated that Tom may have found the diadem before he went to work at B&B—most fans seem to want to believe that the Diadem was altered before the Cup and Locket. My position is that relying on speculation by the characters is ill-advised, and it is better to look at what is likely and reasonable. Apparently, Dumbledore himself was “wrong” about what murder was used to create the Ring, and it’s not as if Harry has a perfect track record with his speculations! The symmetry of it being fifth destroyed/fifth created, plus the fact that it did not fight its destruction, points against his correctness in this idea, but reason also points against it.

So what, then, is likely and reasonable, as regards the discovery of the Diadem? Well, for my part, I do not think for one second that it would be possible to locate such a comparatively tiny item over the course of a single summer. “A forest in Albania” is a very wide range, and we must remember that this object was stashed inside a tree almost a millennium ago—indeed, a tree that was already hollow. That tree was certainly decayed into dirt by the 1940s. The diadem was buried under centuries of dirt. Tom had to pursue a magical archeological dig, effectively. I will accept that it could make its presence felt by magic, but it would have to have a range, and I also think it would have to have someone who was specifically looking for it. I do not believe that Tom found this object in the summer between his graduation and the beginning of his tenure at B&B.

Not to mention that, even for someone as brilliant and well-known as he, it would be a bad idea to simply disappear off the face of the earth for an unknown period of time, searching for this item, and then try to return as Tom Riddle and hunt down the other two. He wouldn’t have known how long it would take him to find the thing. Better to pursue the object(s) that seemed more likely to turn up in Britain and, indeed, which may even have had a paper trail indicating a record of sale. The Diadem would wait for him. It’s not as if anyone else even knew where it was except a ghost, and she wasn’t talking.

It makes a lot more sense that he didn’t begin to look for the Diadem until after he quit that job. I think it was probably around this time that Tom's appearance became profoundly unnatural.  Even if I am wrong about the date that he made the Ring into a Horcrux, he certainly would have done so by the time he started to work for Borgin and Burkes, and he still looked normal even with his soul in three parts.  Indeed, the depiction of the Locket's inside in Deathly Hallows was of the dark eyes of Tom Riddle.  Most likely, he began to look abnormal after creating his third or fourth Horcrux, and he knew then that he couldn't remain in public in the Wizarding world.  He might also have felt that he would fall under suspicion in Hepzibah's death after the theft of her treasures was discovered.

He decided then to track down Ravenclaw's diadem, amass a following, and work on plans for how to get his hands on the last relic that he wanted, the sword of Gryffindor.

In Order of the Phoenix, Professor McGonagall reveals that she has been a teacher at Hogwarts for 39 years as of December.  The year that she says this is 1995, so she came on staff in 1956.  She would have replaced Dumbledore as the Transfiguration teacher, so this is likely when Dumbledore became Headmaster.  Additionally, when Voldemort reappears—looking white, waxy, and abnormal—and goes into the school to meet Dumbledore, it is ten years after Riddle disappeared.  Harry is convinced in Deathly Hallows that Voldemort hid the Diadem of Ravenclaw in the castle before or after this meeting, and I see no reason for him to be wrong about this.  It’s a bit odd that he would have hidden this Horcrux so long before he apparently hid any of the others, but he may have specifically wanted to get this one off his hands because of the sensational nature of it. I do not think that any of the Death Eaters ever knew that he had this particular object in his possession--—unlike every other Horcrux that he had, incidentally. For all Voldemort knew, this was possibly the only opportunity that he, personally, could have in the foreseeable future to dump the Horcrux inside the castle.

Indeed, Voldemort did not have another opportunity (that we know of) to enter the castle again until after his first fall, when he possessed Professor Quirrell, and if he had waited that long, then where was the Diadem while he was out of commission?  He could hardly keep it with him in disembodied partial-soul form. No, Harry was correct in this case.  This means that the Diadem was made into a Horcrux some time in the late 1940s or early 1950s, depending on how long it took him to find it in the forest.

A Failed Plan, a Change of Mind, and a Mission

Voldemort had created five of his intended six Horcruxes within 12 years after leaving school.  Yet he did not attempt to make his sixth until 1981, 25-35 years later.  Why would he have waited so long?  The Prophecy was not made until 1979 or 1980.  Voldemort would not have waited decades to complete his set in the off chance that a Prophecy might be made about someone who could kill him.  What I suspect is that Voldemort was determined, through all those years, to get his hands on Gryffindor's sword.  I also think that Voldemort wanted to complete his set of Horcruxes with a highly significant murder:  the murder of Albus Dumbledore.  And after decades, he was still being thwarted on both counts.  This leads me to believe that the sword was in Hogwarts and he knew it, but he had no workable plan for how to get at it.  For goodness' sake, the man was able to track down an artifact that had been lost for some 900 years.  Years later, he followed the trail to the Elder Wand. Voldemort has a very good track record of finding hidden things that he wants, despite the apparent odds.  And it wasn't in the Ministry, or some mole would have tipped him off to that. We cannot guess as to when the last crisis at Hogwarts occurred in which a Gryffindor had the opportunity to put on the Hat and call for aid. It really can't have been that common, and the persons most likely to have done it would have been professors, after all. (I'd love to have been a fly on the wall at Griphook's when Neville summoned the sword in the heat of battle! Since it apparently isn't stored in a magical hyperdimensional space when it is not in use, it must just vanish from wherever it is when someone calls for it.)

Tom really did want to control Hogwarts.  It was his first home.  I think that his intentions in asking Dippet for the Defense Against the Dark Arts position were multiple:  He wanted to manipulate young minds, he wanted to have a place from which he could easily and safely deploy his Diary, he wanted to get closer to the sword, and he wanted to be in a position to kill Dumbledore and eventually replace him as Headmaster.  As I have stated, I believe that he intended to work at Borgin and Burkes as soon as he heard about the locket.  I think he asked Dippet for the job upon graduation in order to plant the seed in the old Headmaster's mind that he was interested.  He never expected to get the job immediately.  His original plan likely was to track down the Slytherin and Hufflepuff relics, go to Albania and find the Ravenclaw one, amass a following, then return to Hogwarts as a teacher while Dippet was still Headmaster and kill Dumbledore, using the sword for his last Horcrux.  Dumbledore, as has been said, was the only wizard he ever feared.  His death would have been perfect, from Voldemort's point of view, for his last Horcrux, and his hoped-for use of a Gryffindor artifact that had been in Dumbledore's possession would have added insult to injury. Voldemort certainly would have been capable of setting up a situation in which someone from Gryffindor called for help. He probably intended to have the Hat removed from service at some point after he'’d gotten the Sword (and he would have been right to do so; it is a horrible idea to sort 11-year-old children into groups that reinforce their most dominant inclinations at the expense of all others), which would mean that there would not be any more Gryffindors to call for help.

I'm reminded that Voldemort did get Dumbledore alone that winter's night when he asked for the job.  Why didn't he just kill him then?  There are two possibilities:  he may have been dead-set on using the Sword, and the Sword wasn't around; or he may simply have chickened out.  We don't know for sure whether he had yet been in a fair duel with another witch or wizard (or what passes for fair when one person is protected from death).  He had killed people who couldn't defend themselves, and had murdered Mrs. Smith either by poison or by an Imperius Curse to her house-elf, neither of which qualified as a head-to-head fight.

In any case, Tom failed to get the sword and failed to kill Albus.  Then he heard word of the Prophecy in (I suspect) late 1979, possibly early 1980, and decided that it would be easier, and just as fitting, to kill the prophesied child, and to use either the snake or some unknown item for the last Horcrux.  But before he did that, he decided to protect the Horcruxes that he had already made.  I think he heard the Prophecy and decided after hearing it to hide them for safety's sake.  The Diadem was already hidden in Hogwarts.  The Ring may also have been hidden by this time; we do not know.  But we do know that he hid the Locket and the Diary shortly before his fall, the Locket first, it would seem.  Regulus Black died in either 1979 or 1980, soon after Voldemort had taken Kreacher into the cave to deposit the Locket.  We also know, from Dumbledore, that Voldemort gave the Diary to Lucius Malfoy shortly before his disappearance in 1981.

As for the Cup, it had to have been in Bellatrix's vault from before his first fall.  Bella was born no earlier than 1951.  (This is the date given on the Black family tree for her year of birth, but if this is true, it contradicts Sirius Black's statement that Severus Snape was in school when Bellatrix was.  With the new information in Deathly Hallows giving James and Lily's (and therefore Snape's) birth year as 1960, Bellatrix would have finished before Snape started.)  Bella would therefore have finished no earlier than 1969.  Dumbledore says in the very first book, in 1981, that "we've had precious little to celebrate for eleven years."  This means that Voldemort's rise to power began in earnest around 1970.  At some point in the 1970s, Bellatrix joined the Death Eaters, married Rodolphus Lestrange, and gained access to the Lestrange family vault.  Given this timeline, I find it likely that Voldemort gave her the Cup around the same time that he hid the Locket and gave Malfoy the Diary.  If he hadn't already, he would have hidden the Ring as well.

There is a very serious issue with Nagini as the seventh Horcrux to be created.  As we know from DH, Voldemort's soul was so unstable that it blew apart when he attempted to kill Harry, and part of it attached to him, creating an unintentional sixth Horcrux.  But if he was so unstable that he was flying apart after five Horcruxes, how could he have created a seventh one?  He didn't get the soul part back when the Diary was destroyed.

For this reason, I had assumed that Dumbledore was wrong when he said that Voldemort had made his last Horcrux some 13 years after his defeat.  However, with the new information that Bertha Jorkins was the death, this introduces a problem.  Also, in the Priori Incantatem sequence in Goblet of Fire, there is no spell regurgitated prior to the figure of Bertha that looks suspicious.  Harry was not paying attention to Voldemort's wand between the time that Frank Bryce's shade appeared and the time that Bertha's appeared, but the regurgitation of the other curse would have occurred during this time.  Whatever it is, it was not distinctive enough to distract Harry's attention from what Bryce was saying to him.  And as for his ability to make another Horcrux in the first place, the only explanation I have is that the detaching and encasing spell is more precise, being tailored for that specific purpose, than the chaotic rebounding Avada Kedavra that blew Voldemort apart at Godric's Hollow, so he was able to make a Horcrux with it despite the extremely fragile nature of his soul.

There is a minor debate within the fan community about what death caused the unintentional sixth Horcrux.  The answer is quite simple:  It was Voldemort's.  Evidently, that particular AK caused his soul to shatter because of a combination of things—the intent to kill an innocent, defenseless baby was metaphysically worse than the intent to kill an adult; the curse that struck Voldemort was a rebounding AK, and rebounding curses have a documented history of doing far worse damage than straight-on curses; and Voldemort was defying the blood magic that he had activated by killing Lily.

New thoughts as of 8/2013: Well, after a rereading of official canon, I had a couple of issues cross my mind that I hadn't really thought much about before. One of them is, to some degree, related to the essay about the Killing Curse, but since it does specifically have to do with the matter of Horcruxes, I'm going to put it here. It is this: Why, exactly, should murder -- and ONLY murder (based on Dumbledore's conversation with Snape regarding his planned death) -- tear the murderer's soul, and how does it happen? Does it always split a soul into two pieces, or could it cause a rip but not a detached fragment? And is there a way to control it?

I think a clue comes from the book Hermione finds that talks about Horcruxes. To "put oneself back together" requires intense remorse. Presumably remorse could also be used to heal damage caused by the act of murder when no Horcrux was created from it. Remorse, however, is not a spell. It is an emotion. How can it be that a magical object could be dismantled, and the results of Dark magic be undone, by an act that doesn't involve magic?

Or does it involve magic?

In fact, I have come to the conclusion that, in matters of Dark magic in the Potterverse, some acts often DO carry a magical power of their own even when they are not properly spells. Soul splits can be mended and Horcruxes can be taken apart by acts of remorse. Ron Weasley supposedly "had to" wield the sword of Gryffindor to destroy the Locket since he got it out of the pool, and Harry instinctively knows that "certain acts" have an "incalculable power." Intent matters for Dark and wandless magic. Is it not reasonable to postulate that, if the murderer's intent is to create a Horcrux, the damage to his or her soul WILL be in the form of an actual division rather than just a tear, because that's what he or she WANTS? And that's why a multiple-murderer like Voldemort can know with certainty exactly whose deaths he used to make the things.

As to why murder, but not other kinds of killings, will cause damage to the killer's soul, I think one can also invoke "intent matters" as explanation. (We know that assisted suicide apparently doesn't have to cause a split unless the person doing the killing sees it as murder. We don't know if killing in self-defense, the defense of someone else, accidentally, or as a duty of war will cause damage, though they might--just probably not a complete division.) Consider: 1) Murdering something with a soul results in the soul leaving its body. 2) Beings must have souls in order to make conscious decisions. In this view of things, the body is just another instrument for the actions of a conscious soul. If one soul intends to dispatch another against the victim's will, the "incalculable power" of ripping another soul from its body causes damage to one's own soul.

The other issue I thought of is this: If Voldemort intended to create a Horcrux from the death of Harry Potter, he must have had some object in mind to use for it. We are led to think we should have no idea what that object was. This issue was completely dropped in the final book. Rowling never had her characters investigate the scene of the event when they had the chance; they just looked at the old house and moved on. The memorial marker may not have been charmed against graffiti, but I cannot believe that the site itself was not magically protected against theft and tampering. If Voldemort had brought an object with him, then it should still have been there.

Unless it was an object that was magically moved between the time that Voldemort was blown up and the time that Harry showed up at the house. Perhaps, say, an object that was magically tied to another object, which had the ability to summon it from wherever it happened to be, given the right circumstances. And it was a form of magic that overrode other charms and protections.

...Yes, I now think Voldemort did get his hands on the sword of Gryffindor at last. Say what?

Well, why not? He had Snape at Hogwarts. Snape had been there for a couple of years. Snape was a Slytherin, yes, but we know he could still touch and handle the sword. He just couldn't pull it out of the Sorting Hat. And as for the Sorting Hat's connection to the sword, as far as we are given to tell, it only summons the sword from its present location in space when a Gryffindor puts on the hat and calls for help. There is NO evidence whatever that the sword then disappears into the ether after the crisis has passed, and plenty that it does not! As far as we can tell, after Harry pulled it out of the hat in his second year, it was given to Dumbledore and kept in his office for several years later. It is then, at the end of the seventh book, summoned by Neville from some unknown goblin-protected location. We don't know where it was prior to being summoned by Harry, but at a guess, I'd say it might have been buried in rubble at a certain ruined house in Godric's Hollow. Dumbledore certainly didn't know where it was until Harry put it in front of his eyes.

At a stretch, it might have already been there. It's certainly conceivable that James Potter got hold of the sword at some point in his school years and just decided to keep it. However, I'm more inclined to think that Snape passed it to Voldemort once Voldemort made the plan to kill Harry Potter and requested the sword. It had probably been kept somewhere in the school for years. Where else could it have been, really? The Sorting Hat can summon it for any Gryffindor during a time of crisis or need. This is not exactly secret knowledge; the Minister of Magic--a former Auror, not necessarily an expert in historical artifacts--knew it. Once brought into the school by that method, how could it have left the school except by a member of the staff determined to smuggle it out? It's not like a student who summoned it could steal it under everyone's noses. The Hat itself, after all, is kept in the Headmaster's office except during the Sorting. And if a staff member did steal it, the obvious solution would be to have a Gryffindor teacher put on the Hat and call for the sword. It's difficult to place the sword outside the school for any long period of time, and remarkably easy to imagine Voldemort demanding that Snape pass it to him prior to his attack on the Potters. (As an aside, yes, Voldemort definitely intended to end the Sorting and put the Hat out of commission. Not a bad idea, actually.)