Anti-Dementor lessons

"A Patronus is a kind of positive force, and for the wizard who can conjure one, it works something like a shield, with the Dementor feeding on it, rather than him. In order for it to work, you need to think of a memory. Not just any memory, a very happy memory, a very powerful memory… Allow it to fill you up…lose yourself in it…then speak the incantation ‘Expecto Patronum.’"

- Remus Lupin

In 1994, Remus Lupin, then-Professor of Defence Against the Dark Arts offered to teach Harry Potter how to perform the Patronus Charm. These lessons took place in the History of Magic classroom using a Boggart that Lupin had managed to locate hiding inside Filch's filing cabinet, which he then placed inside of an old packing case. When the packing case was opened in front of Harry, the Boggart would take the form of his worst fear, a Dementor, on which Harry would then attempt to perform the Patronus Charm. Although the Dementor was fake, it still produced similar effects on Harry, and Lupin would give him some chocolate after each lesson. Harry took several of these lessons with Lupin before he eventually succeeded in creating a Patronus.

Background information
In the summer of 1993, Sirius Black, the most infamous prisoner in Azkaban, escaped from the prison. When informed of this situation, Minister for Magic Cornelius Fudge took many proactive measures in order to corral Black once more. Among these were informing the Muggle Prime Minister and deploying the Dementors into the countryside to search for him.

At the beginning of the school year fearing that Black might attempt to kill Harry Potter, Fudge dispatched the Dementors to protect Hogwarts School of Witchcraft and Wizardry and search Hogsmeade village. On 1 September, the Hogwarts Express was searched by the Dementors. When a Dementor reached Harry's compartment, Harry was uncharacteristically affected by its presence. He began to have a fit and could hear a woman screaming in his head. Ginny Weasley was also greatly affected, but not to the extent that Harry was, as he passed out from the experience. Professor Lupin drove off the Dementor by using the Patronus Charm. Once the Dementor was gone and Harry and his friends had eaten some chocolate, they all began feeling much better. However, the whole experienced unnerved Harry that none of the others had been as greatly effected as he had been.

Word spread quickly about Harry's reaction to the Dementors on the train, causing a great deal of taunting from the other students over the incident, especially Draco Malfoy and his cronies. Harry did not have another run in with a Dementor until his first Quidditch match versus the Hufflepuff Quidditch team. The Dementors invaded the match seeking to feast off the high running emotions. This time instead of just one Dementor, Harry was faced with at least a hundred of them, and was once again greatly affected by their presence and passed out falling fifty feet from his broom.

The lessons


Remembering that Professor Lupin had somehow driven the Dementor away on the train, after Harry was released from the Hospital wing, he asked if Professor Lupin would teach him how to fend off the Dementors. Lupin was initially reluctant, but after seeing Harry's determination, he relented. However, Lupin told Harry that their lessons would have to take place after the Christmas holidays as he was feeling under weather.

They began their first lesson early in January in the History of Magic classroom. Professor Lupin had procured a Boggart from Caretaker Filch's office. When he explained to Harry that the Boggart would take the form of a Dementor and that it would create a more real experience, Harry was apprehensive, but tried to sound reassured. Before he released the Boggart, Lupin taught Harry the incantation, Expecto Patronum, and gave Harry a short lecture on the Patronus Charm and its effects. Then he told Harry to concentrate on one single happy memory, and when Harry informed him that he was ready they tried it once without the Boggart, and Harry was able to conjure a thin wisp of vapour. Next, Lupin unleashed the Boggart.

Harry tried many times to conjure a Patronus, but he failed and soon collapsed. Lupin fed him some chocolate and asked if Harry still wanted to continue. Harry, of course, was not going to quit, so they tried again after Lupin told Harry to pick a stronger memory. The result was the same, but Harry did not want to stop, even though Lupin was having reservations. Once more they tried, after Harry had picked another memory, and Harry managed to produce a shield. He was putting all of his strength into holding the Dementor-Boggart at bay, when Lupin banished it. Lupin was happy that Harry had managed the spell, but it cost Harry all his strength.

After a few lessons, Harry lamented at his lack of progress. He remarked that he had hoped he would be able to conjure something that would drive the Dementors completely away instead of just temporarily shielding him, as holding on to the shield took so much out of him. Lupin told him that a true Patronus would do just that, but for a thirteen year old wizard Harry was doing extremely well and should be able to, at the very least, reach the ground should the Dementors made another appearance at a Quidditch match.

During the next Quidditch match, Harry was again faced with what he thought were Dementors, he reacted instinctively and cast the Patronus charm just before grabbing the snitch, winning the game for Gryffindor. Afterward, he found out that what he thought were Dementors were actually Malfoy and his cronies trying to scare him, their plan backfiring on them when instead of scaring Harry they themselves are scared by Harry's first corporeal Patronus chasing them down.

Aftermath
"If I'm proud of anything I've done this year, it's how much you've learned.... Tell me about your Patronus."

- Professor Lupin addressing Harry's Education

Harry would be called upon to use the Patronus Charm in a life threatening situation soon enough. In June, Harry discovered that his godfather, Sirius Black, had not, in fact, betrayed his parents, but it had been Peter Pettigrew who performed that dastardly task. For a glorious half hour, Harry believed he would finally be rid of the Dursley family. That was snatched away when the full moon rose, and Lupin who had forgotten to take his Wolfsbane Potion transformed into a werewolf. Amidst the commotion, Pettigrew managed to transform back into a rat and escape. Sirius was injured trying to protect Harry and his friends from Lupin so when the Dementors found him by the lake, he was unable to defend himself or to get away. Harry and his friend Hermione Granger tried to defend Sirius from them, but after holding out briefly, Harry's Patronus shield was overcome by the Dementors, one of whom tried to perform the Dementor's Kiss on Harry. The Dementors were driven away by a powerful Patronus, but Harry could not identify his saviour. When Harry and Hermione used the Time-Turner to go back in time, Harry discovered that it was he who had cast the Patronus that saved his, Hermione, and Sirius's lives. He then cast the spell driving nearly one hundred Dementors off.

The following morning when Harry went to speak with Professor Lupin who Harry had just discovered had resigned, Lupin asked him about his Patronus. After Harry told him, Lupin confirmed Harry's supposition that his Patronus was "Prongs", and he told Harry how proud he was to have taught Harry so much.

Behind the scenes

 * In the film adaptation of Harry Potter and the Prisoner of Azkaban, Harry only took one of these lessons from Lupin instead of the several mentioned in the book.
 * In the film version, the lesson takes place in the Astronomy Room (the set for which had been previously used for Dumbledore's office in the second film), instead of the History of Magic classroom as in the book version.
 * In the film, Harry was able to produce a non-corporeal Patronus on only his second attempt.

Appearances

 * Harry Potter and the Prisoner of Azkaban
 * Harry Potter and the Prisoner of Azkaban (film)
 * Harry Potter and the Prisoner of Azkaban (video game)