First lesson WAS: Re: Marietta, was Slytherin's Reputation

[Carol]

No: HPFGUIDX 185898

Annemehr wrote:
> Snape certainly was up to something.
> 
> Supposedly, Draco was supposed to cast a spell *at Harry,* who would
try to block it with Protego.  And it wouldn't really have mattered
how advanced the spell was (aside from an AK), if only Harry knew how
to cast Protego.
> 
> But Snape told Draco not to cast a spell at Harry, but to conjure a
 snake instead.  As far as we know, Protego doesn't protect you from
animals.
>
Carol responds:
Protego is a Shield Charm that "cast[s] a temporary invisible wall
around [the caster] to protect him from minor curses" (GoF 608), which
is all that the twelve-year-old Draco would be capable of casting.
We know that it works against Legilimens, which is not a "minor curse"
but a mind-reading spell, and in that instance, the spell rebounds on
the caster, so that Snape's own memories are revealed. 

The Ministry recommends it as a defense against the Death Eaters
(though it won't work against Unforgiveables). That the barrier
created by Protego does more than block the "minor to moderate hexes
and jinxes" mentioned by the Twins in connection with their Shield
Cloaks and Shield Hats (HBP Am. ed. 119) is shown when Harry casts a
Protego to protect Ron from Hermione in DH: 

"'Protego!' The invisible shield erupted between Ron and Hermione. the
force of it knocked her backward onto the floor. . . . 'I knew you
weren't dead,' bellowed Ron, . . . approaching as close as he could
with the Shield Charm between them" (DH Am. ed. 580-81).

If neither Hermione nor Ron can get through the conjured wall between
them, a conjured snake could not get through the conjured wall around
Harry that would have been created had Lockhart told him how to cast a
Protego.

Carol, wondering what Annemehr thinks that Snape was "up to" given
that we know he was protecting Harry