The Core of the Elder Wand and other new JKR explanations

[pippin_999]

No: HPFGUIDX 179714

> Carol responds: 

 How could Draco, who
> seems to be afraid (like most people) of dying have been the
> (unwitting) master of the wand, and why did it work perfectly for
> Voldemort (who killed loads of his own DEs with it and used it to
> create Nagini's bubble) when he was more afraid of death than anyone
> in the WW? 

Pippin:
 As JKR says elsewhere, this sort of deep magic is not 'scientific' -- 
intent and moral purpose matter. Despite Dumbledore's offer of 
sanctuary, which after all did not look very promising, Draco was 
choosing to face death when he lowered the wand. I don't know
how the wand "knows" these things. It's magic!

I couldn't find the thestral question directly from Jo's site. Here's
a link if anyone else is having that problem.

http://www.jkrowling.com/textonly/en/extrastuff_view.cfm?id=25

Carol:
I found his statement to Snape that it wasn't performing
> exceptional magic for him bewildering, in any case.  If you want
> someone dead and they die, isn't that sufficient? How do you perform
> an exceptional AK? And what, exactly, was inadequate about Nagini's
> bubble?

Pippin:
I've been wondering if the bubble spell would have defeated an AK.
I doubt it. I think that's what Voldemort was talking about. He would
have tested it, not on Nagini obviously. 

This has implications for Harry's decision that he won't be the one
to  kill Nagini. I think having learned that he could enjoy torture
well enough to perform the cruciatus curse, Harry was unwilling to 
find out whether he could do an AK.

Snape might have become the master of the EW if he had
decided to fight Voldemort, IMO. He does raise his wand, but
IMO chooses death rather than blow his cover, with the
risk that Voldemort will find a way to break through Snape's
occlumency once he's sure it's being used against him. 

Pippin