Does the canon explicitly address which of the following 3 acts cause a piece of Voldemort's soul to split off and embed into Harry?

  1. Murdering Lily
  2. Trying to murder Harry (e.g. would the soul have split even if he didn't get hit by rebound Avada Kedavra?)
  3. Getting hit by rebound Avada Kedavra - if he didn't, the soul piece would NOT have split off.

Canon means books, JKR interviews or Pottermore.

I'm very specifically interested in information OTHER than Dumbledore's guess stated in chapter 24 ("The Prince's tale") of Deathly Hallows: ...

“Tell him that on the night Lord Voldemort tried to kill him, when Lily cast her own life between them as a shield, the Killing Curse rebounded upon Lord Voldemort, and a fragment of Voldemort’s soul was blasted apart from the whole, and latched itself onto the only living soul left in that collapsed building. Part of Lord Voldemort lives inside Harry, and it is that which gives him the power of speech with snakes, and a connection with Lord Voldemort’s mind that he has never understood. And while that fragment of soul, unmissed by Voldemort, remains attached to and protected by Harry, Lord Voldemort cannot die.“

... and Chapter 25, "King's Cross":

“You were the seventh Horcrux, Harry, the Horcrux he never meant to make. He had rendered his soul so unstable that it broke apart when he committed those acts of unspeakable evil, the murder of your parents, the attempted killing of a child. But what escaped from that room was even less than he knew. He left more than his body behind. He left part of himself latched to you, the would-be victim who had survived.”

The reason is that this quote doesn't seem to very clearly point to causality, and also it was just Dumbledore's guess. I'm hoping one of the JKR sourced information sources would clarify this.

  • As a side note - I don't care if the reason was simply a specific act among those 3, or simply the fact that "cumulative amount of evil acts" reached some threshold when he did them all together. Either way, one of the 3 events I listed was the trigger. Oct 31, 2013 at 13:47
  • I don't think getting hit by the rebound Aveda Kedavra alone is the trigger to split your unstable soul. Aveda Kedavra is just a curse which kills the person being hit. Since the killing curse is the most sinister of all and it has to be cast with the real intention of killing someone to cause any affect, therefore, the mere effective casting of the Killing Curse(supreme act of evil) is the reason for the instability of the soul and its splitting. Oct 31, 2013 at 14:25
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    possible duplicate of Is Murder a necessity to detach your soul? Oct 31, 2013 at 14:33
  • @DVK: Is Murder a necessity to detach your soul?. An Effective Casting of the Killing Curse is the Reason for detachment of your soul. That is what i think. Oct 31, 2013 at 14:44

1 Answer 1


JKR: So because Voldemort never went through the grotesque process that I imagine creates a Horcrux with Harry, (SU: Mm-hm.) it was just that he had destabilized his soul so much that it split when he was hit by the backfiring curse. And so this part of it flies off, and attaches to the only living thing in the room. A part of it flees in the very-close-to-death limbo state that Voldemort then goes on and exists in.

That's as canon as it gets: a Word of God quote saying that it was specifically the backfiring curse that caused Voldemort's soul to split.

  • Well, I may be wrong, but she says when and not because, and causality is still not clear. But that allows the more natural possibility @Madeyedexter points out above. I think we can conclusively observe that spells or magic in HP Universe do never affect souls (as Muggle weapons don't in ours, if you believe in the same concept of soul as me); only intentions and acts do. While this is not elaborated in any of the relevant places in canon, Dumbledore's insights, Slughorn's knowledge and Hermione's findings together suggest the folowing theory as has been pointed out earlier on this site: Jun 30, 2014 at 12:19
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    Committing a murder may always split the soul, but the pieces may not separate from the body (and may even reattach with time, it has been speculated here). What the Horcruxification spell does might be detaching the (smaller) part to be encased in a container (before they merge back, may be). Being so destabilised, Voldemort's soul split and detached itself readily when he attempted his third murder, that of an innocent child, that night. Jun 30, 2014 at 12:20
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    @NUnnikrishnan Well, think about it - the broken pieces of Voldemort's soul are only held together by his body. His body was utterly destroyed (quite unlike the usual effect of the Killing Curse; this was no rebounded curse, no matter what Dumbledore or Rowling says), leaving the pieces of his soul desperate to find any place to hold on to - some might have found their way to another horcrux, some claimed the nearest living body that could offer little resistance. Whatever the "rebounded" curse, it didn't strike at the soul - it just destroyed what was holding the pieces together.
    – Luaan
    Dec 13, 2016 at 9:44
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    @Luaan fair point. Voldemort was already shattered to pieces. It's like soaking a jar you just glued back together in acetone. The jar is probably not going to be affected by the acetone, but the glue will dissolve and the pieces will separate. It's probable that Voldemort's soul was already long broken from many many more previous murders. So, the only logical thing to presume is that Voldemort's death merely freed his shattered soul to crumble into pieces that went running for whatever they could find. My question though is how Harry got turned into a horcrux by accident. Seems a bit... odd.
    – user64742
    Dec 14, 2016 at 5:49
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    @NUnnikrishnan No, not on Sci-fi.SE. Questions and answers that do not target canon are perfectly fine and accepted. And just because the author says something doesn't necessarily mean it's canon - different franchises have different rules (or don't have canon in the first place), and it still must be self-consistent; contradictions are not very useful for explanations and settings in general. We know what the Killing Curse does - it doesn't do any visible damage to the victim. Whatever happened to Voldemort, it wasn't the effect of the Killing Curse (though it might have been related).
    – Luaan
    May 4, 2017 at 17:45

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