prior incantato/priori incantatem

[lupinesque]

No: HPFGUIDX 35881

Eloise wrote:

> To me Prior Incantato is the spell that works on the same principle 
as the 
> natural phenomenon, Priori Incantatem. The latter is a wand forcing 
the last 
> spells out of its brother wand (and it is only capable on its own 
of doing it 
> to its brother), whereas a wizard in conjunction with his wand can 
use Prior 
> Incantato to force the last spell out of *any*  other wand.

This makes it sound as if Prior Incantato is more powerful, but when 
I read "The Dark Mark" I assume that the "echo" Amos Diggory gets is 
much weaker than the ones Harry's wand impels out of Voldemort's.  
E.g. one could not use Prior Incantato to create an echo of someone 
who has just been Avada Kedavra'd and have a quick chat with 
him/her.  Too bad, because it would be invaluable for police work if 
you could ask the victim of a murder all about how the crime came 
about.  Instead I imagine a fainter echo, just a wee little wisp that 
indicates what happened with the wand, nothing more.

I can cite no canon for this other than the fact that Sirius's 
response to Priori Incantatem makes it clear that it is very rare.  
He has never heard of it.  Part of the reason for the rarity may be 
that the spells have to be said simulaneously; it is "against one 
another" that the wands can't work properly; that doesn't mean that 
Voldemort can't cast an effective spell against Harry just because 
Harry happens to be *holding* a brother wand.  Had Harry been a 
second later with his "expelliarmus!" he'd be dead, IMHO.  But the 
other reason it's rare is that it's something only a brother wand can 
do.  Therefore what Amos Diggory does to Harry's wand can't be the 
same thing; it must be lesser in some way.

Another distinction that *is* supported by canon is that the spell 
Amos Diggory does seems only to be able to conjure up the very last 
spell performed by the wand.  Say a quick "lumos" after you've 
conjured the Dark Mark and no one will be able to dig out the 
evidence, unless he/she has the brother to your wand.

As for the Latin difference between the two PIs, I'm clueless.  We 
have plenty of Classics scholars around here, though.

Amo, Amat, Amy Z