Shield Charm

"You wouldn't believe how many people, even people who work at the Ministry, can't do a decent Shield Charm [...]"

- George Weasley

The Shield Charm (Protego) as a term applied to several varieties of charms that create a magical barrier to deflect physical entities and spells. Conjurations may sometimes rebound directly off it back towards the caster, or, in other cases, may ricochet off in other directions or dissipate as soon as they hit the shield.

This was also the subject of a question of the Theory of Charms O.W.L. in 1996.

Casting and effects
When cast, a bright blue transparent shield appears where the casters wand is pointed providing a protective barrier between themselves and their attacker. The only spell the Shield Charm can't defend against is the Killing Curse, since it's unblockable.

The Shield Charm is a moderately difficult spell. Fred and George Weasley realised that most adult wizards, even those employed by the Ministry of Magic, could not produce a functional Shield Charm (something that not only could Harry Potter accomplish at age fourteen but, also impart to members of the D.A.). They used this to their advantage when marketing their line of protective clothing (hats, cloaks, etc.), upon which permanent Shield Charms were cast.

The incantation for the simplest Shield Charm spell is Protego. Incantations for other varieties of the Shield Charm include Protego Duo, Protego Horribilis, Protego Totalum and Protego Maxima.

Harry Potter
"His Shield Charm was so strong Snape was knocked off-balance and hit a desk."

- Harry Potter's impressive mastery of the charm



Other

 * In 1484, Hannah Cockleford used the Shield Charm to protect a Muggle boy named Edmund Gaddlegate when he was forced to joust with the Earl of Paunchley.
 * Gilderoy Lockhart presumably attempted to demonstrate this charm, or something similar, to Harry during the first meeting of his duelling club, but all he truly wanted was to twirl his wand fancifully, which failed spectacularly, dropping his wand in the process.
 * This charm was among those that Harry taught the members of Dumbledore's Army in his fifth year.
 * In 1996, Dolores Umbridge used a shield charm to protect herself from the centaurs' arrows in the Forbidden Forest.
 * During the Battle of the Department of Mysteries, the fighting Death Eaters cast many Shield Charms to protect themselves from Dumbledore's Army's Stunning spells.
 * Hermione Granger managed to cast this nonverbally in their first sixth year Defence Against the Dark Arts lesson.
 * Remus Lupin, Nymphadora Tonks, and various other guests at Bill Weasley and Fleur Delacour's wedding in 1997 cast shield charms after Kingsley Shacklebolt's Patronus arrived to warn those at the Burrow that Lord Voldemort had taken over the Ministry of Magic.
 * Hermione Granger cast the Shield Charm in 1997, when Harry and Ron got into an argument during their search for the Horcruxes. Hermione cast the shield before they could draw their wands against one another. When Ron subsequently left, Hermione was hampered in trying to follow him and persuade him not to leave by her own shield.
 * Severus Snape cast this charm to deflect Harry Potter's spells during their brief duel after he killed Albus Dumbledore.
 * Severus later used a Shield Charm during his duel with Minerva McGonagall, knocking her off her feet.
 * Lord Voldemort used a Shield Charm to defend himself during his duel with Albus Dumbledore.
 * Voldemort also used many Shield Charms when duelling Harry Potter and many others during the Battle of Hogwarts.

Practitioners

 * Dolores Umbridge
 * Dumbledore's Army
 * Harry Potter
 * Hermione Granger
 * Sirius Black
 * Remus Lupin
 * Severus Snape
 * Bellatrix Lestrange
 * Kingsley Shacklebolt
 * Nymphadora Tonks
 * Lucius Malfoy
 * Lord Voldemort
 * Ginny Weasley

Known Variations

 * Protego Duo
 * Protego Horribilis
 * Protego Maxima
 * Protego Totalum

Etymology
Latin protego, "I cover" or "I protect".

Behind the scenes

 * In the films, Shield Charms are used in nearly every duel shown, almost always used non-verbally and usually accompanied by a parry-like wand movement.
 * Also in the films, Shield Charms are shown to be able to deflect material objects such as arrows which were shot using a bow. Also it has shown to be able to withstand dragon fire from a Hungarian Horntail as seen in Harry Potter and the Deathly Hallows:Part 1 The Video Game.
 * The book depicts the Shield Charm as only being capable of repelling "minor to moderate curses and hexes", although Harry Potter uses it to block the worst effects of Antonin Dolohov's curse in the Department  of Mysteries. However the film implies the Shield Charm to be significantly more powerful in that Harry is able to use it to completely deflect powerful curses cast by Voldemort himself.
 * In the early video games, Expelliarmus functions as a shield charm, due to a lack of enemies to Disarm. In these games, Protego is absent.
 * In the books Protego is also able to keep two quarreling wizards from going at each other when a shield is cast between them.
 * In Harry Potter and the Deathly Hallows: Part 2, Protego is shown several times to be able to block the Killing Curse. Harry blocks multiple Killing Curses from Voldemort during their final duel and Bellatrix Lestrange blocks four Killing Curses while duelling Molly Weasley. According to the books this is incorrect as the Killing Curse is "unblockable" which is the main reason for its particular infamy, but within the context of the films the fact is never mentioned. As the Killing Curse would instantly end any duel if it were unblockable, this might just be done for dramatic effect and for longer duels.
 * In Harry Potter for Kinect Harry and Voldemort can use this spell against each other in the final battle during Voldemort's Last Stand as they engage in a normal duel.

Appearances

 * Harry Potter and the Goblet of Fire 
 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Order of the Phoenix (film)
 * Harry Potter and the Order of the Phoenix (video game)
 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Half-Blood Prince (film)
 * Harry Potter and the Half-Blood Prince (video game)
 * Harry Potter and the Deathly Hallows
 * Harry Potter and the Deathly Hallows: Part 1
 * Harry Potter and the Deathly Hallows: Part 1 (video game)
 * Harry Potter and the Deathly Hallows: Part 2
 * Harry Potter and the Deathly Hallows: Part 2 (video game)
 * LEGO Harry Potter: Years 5-7
 * Harry Potter: Spells
 * Pottermore
 * Wonderbook: Book of Spells
 * Harry Potter for Kinect

Notes and references
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