What would happen to the Elder Wand if a living Horcrux killed its current wielder?

Question

What happens if a Horcrux (or indeed, any other non-wizard being containing part of a wizard's soul) kills the owner of the Elder Wand?

For example, consider when Dumbledore was still the master of the Elder Wand; suppose Nagini had killed him.
Nagini is not a wizard; since only wizards can wield a wand, it would seem like the Elder wand should remain with Dumbledore forever.
On the other hand, Nagini, as a Horcrux, has a part of Voldemort's soul inside it. Would that be enough for the Elder Wand to change hands?

Answer 1

It would count as Voldemort performing the deed.

We have canonical evidence for this: Nagini was the one who killed Snape, which would have enabled mastership of the Elder Wand to pass to Voldemort (assuming Voldemort had calculated the consequences of his deed correctly, which we should probably assume he had).

Nagini killed Snape on Voldemort's command, but if Voldemort had commanded a Death Eater to perform the deed, then the Death Eater and not Voldemort would have become the master of the Elder Wand. We see this with Draco Malfoy: Voldemort ordered him to kill Dumbledore, but when he Disarmed Dumbledore, the Elder Wand mastership passed to him and not Voldemort.

Nagini is a Horcrux of Voldemort, containing part of his soul. If she had killed Dumbledore, then mastership of the Elder Wand would have passed to the owner of the piece of human soul inside her, i.e. to Voldemort.

See also this answer.

Answer 2

I don't think it would count as Voldemort - after all, Harry was also a horcrux, at the time he won allegiance through Malfoy. Of course, Nagini is acting within Voldie's will, and Harry as his own person, so that might complicate it... but I think the answer is no.

As for what would happen to the wand's allegiance? Harry wins the wand through a duel with Malfoy which happened without the elder wand being present (or even known to be relevant). So it might be the wand will go 'looking' for a wielder among those who last disarmed its previous owner, even if it was a different wand being won at the time. There would almost have to be some mechanism for reuniting the wand and the mastery of the wand, or restarting the claim of ownership, if its allegiance can separate from the wand itself to pass through the second hand defeat of those who might not even know they've won it.

Answer 3

If he used Nagini to kill its master, Voldemort would likely be the master of the Elder Wand.

It seems most likely that if Voldemort used Nagini to kill the master of the Elder Wand, the ownership of the Elder Wand would pass to Voldemort, since Voldemort controls Nagini. To master the Elder Wand requires capturing it in some way from its previous master.

“Which is that the possessor of the wand must capture it from its previous owner, if he is to be truly master of it,’ said Xenophilius. ‘Surely you have heard of the way the wand came to Egbert the Egregious, after his slaughter of Emeric the Evil? Of how Godelot died in his own cellar after his son, Hereward, took the wand from him? Of the dreadful Loxias, who took the wand from Barnabas Deverill, whom he had killed? The bloody trail of the Elder Wand is splattered across the pages of wizarding history.”
_{^{- Harry Potter and the Deathly Hallows, Chapter 21 (The Tale of the Three Brothers)}}

If Nagini was directly ordered by Voldemort to kill Dumbledore, she would then be no different than any tool used to kill. The results would likely be no different than if Voldemort had instead used a spell or a knife to kill the master of the Elder Wand. Voldemort believes Snape to be the master of the Elder Wand, and kills him using Nagini, so Voldemort at least thought that the Elder Wand’s allegiance would pass to him if he killed using Nagini.

“It cannot be any other way,’ said Voldemort. ‘I must master the wand, Severus. Master the wand, and I master Potter at last.’

And Voldemort swiped the air with the Elder Wand. It did nothing to Snape, who for a split second seemed to think he had been reprieved: but then Voldemort’s intention became clear. The snake’s cage was rolling through the air, and before Snape could do anything more than yell, it had encased him, head and shoulders, and Voldemort spoke in Parseltongue.

‘Kill.’

There was a terrible scream. Harry saw Snape’s face losing the little colour it had left, it whitened as his black eyes widened, as the snake’s fangs pierced his neck, as he failed to push the enchanted cage off himself, as his knees gave way, and he fell to the floor.”
_{^{- Harry Potter and the Deathly Hallows, Chapter 32 (The Elder Wand)}}

If Voldemort commanded Nagini to kill Dumbledore in Parseltongue, it would be even more clearly a direct kill by Voldemort. It seems Parseltongue compels snakes to obey those who speak it - basilisks can be controlled by Parselmouths.

“However, since Basilisks are uncontrollable except by Parselmouths, they are as dangerous to most Dark wizards as to anybody else, and there have been no recorded sightings of Basilisks in Britain for at least four hundred years.”
_{^{- Fantastic Beasts and Where to Find Them}}

Additionally, Voldemort has even more control over Nagini than Parselmouths usually have over snakes.

“After an interval of some years, however, he used Nagini to kill an old Muggle man, and it might then have occurred to him to turn her into his last Horcrux. She underlines the Slytherin connection, which enhances Lord Voldemort’s mystique. I think he is perhaps as fond of her as he can be of anything; he certainly likes to keep her close and he seems to have an unusual amount of control over her, even for a Parselmouth.”
_{^{- Harry Potter and the Half-Blood Prince, Chapter 23 (Horcruxes)}}

If Voldemort had Nagini kill Dumbledore, she would have been commanded by Voldemort to do the killing, so she would presumably be no different than any other method of killing, and the mastery of the Elder Wand would pass to Voldemort.