CHAPDISC: DH32, The Elder Wand

[Carol]

No: HPFGUIDX 184762

Potioncat:
<snip>
> But I don't think he knew about Nagini's protecion until we see him 
> in the Shrieking Shack.
>
Carol responds:

Nor do I. He was desperately seeking Harry *before* he knew about
Nagini, wanting to talk to him even while Harry was under the
Invisibility Cloak (before McGonagall attacked Snape). Clearly, Snape
knew that matters had come to a head--Voldemort was about to attack
Hogwarts--and Harry had to find out about the soul bit so he could let
Voldemort kill him, Nagini or no Nagini. Harry notes even then that he
seems distracted, looking around (for him), hardly aware of what he's
doing or saying. 

When Snape sees Nagini in her bubble in the Shrieking Shack, he's even
more aware that time is pressing. He *must* get that message to Harry.
He's hardly hearing what LV says about the wand (maybe the
"extraordinary magic" he mentions is what he's seen performed with the
yew wand?). He doesn't even realize that he's in danger until he
understands that Voldemort desecrated Dumbledore's tomb to get *his*
wand, the Elder Wand, the Deathstick. At that point, he stops
repeating his request to find the boy and reaches for his own wand,
but he doesn't use it. He know that Voldemort can't be killed and that
he has to kill Harry.

At any rate, Nagini isn't the trigger that sets him looking for Harry.
I think that trigger is Voldemort's message that Harry is coming to
Hogwarts and he, Voldemort, will follow.

Carol, sneaking in a post or two before the next chapter arrives