Ousting of Severus Snape

"No! You'll do no more murder at Hogwarts!"

- Filius Flitwick arrives at the duel.

The ousting of Severus Snape was a duel between Severus Snape, then Headmaster of Hogwarts School of Witchcraft and Wizardry, and the Hogwarts Heads of House. After having defeated Alecto and Amycus Carrow on the Ravenclaw Tower, Harry Potter and Luna Lovegood (both under the Invisibility Cloak) along with Minerva McGonagall went down to warn the Heads of House that Lord Voldemort and his Death Eaters were about to siege the Castle in an attempt to get Harry Potter. As they got down, they were stopped by Headmaster Severus Snape and the two teachers engaged in a duel. McGonagall was joined by Filius Flitwick, Pomona Sprout and Horace Slughorn. Now greatly outnumbered, Snape fled into a nearby classroom and flew out of a window.

Background
In the evening of 1 May, 1998, Harry Potter, Ronald Weasley and Hermione Granger returned to the Death Eater-controlled Hogwarts Castle seeking Ravenclaw's diadem, one of Lord Voldemort's Horcruxes. As Harry Potter and Luna Lovegood entered Ravenclaw Tower, Alecto Carrow caught them and pressed her Dark Mark with her finger, thus sending the warning to Lord Voldemort and the other Death Eaters that Harry Potter was in the Castle. Luna Lovegood Stunned Alecto. Amycus Carrow then went to the Tower, and ordered Minerva McGonagall to open the door for him. After Amycus spat on McGonagall's face, Harry Potter cast a Cruciatus Curse on him, smashing the Death Eater into a bookcase. Knowing Lord Voldemort and the Death Eaters would be soon attempting to break into the Castle, McGonagall left the tower with Harry and Luna (the latter two under the Invisibility Cloak) in order to warn the Heads of House and to set up magical defences around the grounds.

The duel
Two floors below Ravenclaw Tower, Harry noticed another quiet set of footsteps, and Headmaster Severus Snape emerged from behind a suit of armour. Seeing only McGonagall, as Harry and Luna were hidden beneath the Invisibility Cloak, Snape discreetly used Legilimency on the Professor and found out that Harry was in the Castle. McGonagall quickly slashed her wand through the air, but Snape cast a Shield Charm that threw McGonagall off balance. She then brandished her wand to a torch on the wall, making it fly off its bracket. The flames became a ring of fire that filled the corridor and flew like a lasso at Snape. Snape promptly turned the descending flames into a great black snake that McGonagall blasted to smoke and turned into a swarm of daggers, which she directed towards him. The Headmaster forced the suit of armour in front of him, thus avoiding the flying daggers that sank into it with echoing clangs.

At this point, Filius Flitwick, Pomona Sprout and Horace Slughorn sprinted up the corridor toward them in their nightclothes. With a squeal, Flitwick raised his wand bewitching the suit of armour to attack Snape. Snape, now greatly outnumbered, sent the suit of armour flying against his attackers and hurtled into a nearby classroom, jumped through a window and flew away.

Aftermath


As Snape flew away, McGonagall informed the Heads of House that Lord Voldemort was coming. The teachers arranged so that they met in twenty minutes at the Great Hall in order to evacuate underage students. Filius Flitwick started casting protective enchantments around the Castle, Minerva McGonagall bewitched the school's suits of armour to man the boundaries, and Pomona Sprout departed for the Herbology greenhouses to retrieve dangerous plants to hold off the Death Eaters and Horace Slughorn went to wake his Slytherins in the dungeons.

Behind the scenes

 * In the second part of the film adaptation of Harry Potter and the Deathly Hallows, this duel has some noticeable differences:
 * Unlike in the novel, Severus Snape hears of Harry Potter's sighting in Hogsmeade and summons all students to a meeting at the Great Hall. Harry Potter, who was in the Room of Requirement at the time of the summons, dresses in spare Gryffindor robes and goes down to the Great Hall blended in with the other students. Alecto and Amycus Carrow are also present, as well as all members of staff apart from Argus Filch. After Snape threatens to severely punish every student who fails to tell him about Harry's whereabouts, Harry reveals himself and members of the Order of the Phoenix back him up. Minerva McGonagall, however, steps up and singlehandedly fends Snape off using a fiery spell. The Carrows are left knocked out as Snape deflects McGonagall spells and they are hurled to the floor.
 * In the film adaptation, Filius Flitwick, Pomona Sprout and Horace Slughorn do not take part in the duel, but all are present in the room and pointing their wands at Snape ready to help McGonagall.
 * In the film adaptation all students witness the duel, unlike the book in which no one seems to have noticed that Snape fled from the Castle until McGonagall tells the student body "he has, to use the common phrase, done a bunk".
 * In the film Snape does not attack back against McGonagall but instead blocks all of her attacks before fleeing.


 * The spell that McGonagall used to turn Snape's transfigured snake into a cloud of smoke may have been Vipera Evanesca.
 * During one of the takes while filming this scene, Alan Rickman, while gesturing with his prop wand, hit his hand against the wires of a camera, dropping his wand and exclaiming "Ouch."
 * "The Sacking of Severus Snape" is the title of chapter 30 of the seventh book, in which the duel takes place. However, this name is technically innacurate, as "sacking" or "dismissal" refers to the termination of employment by the employer, against the will of the employee. Neither of the fighters who banished Snape from Hogwarts were his employers, more so, they were his subordinates.

Appearances

 * Harry Potter and the Deathly Hallows
 * Harry Potter and the Deathly Hallows: Part 2
 * Harry Potter and the Deathly Hallows: Part 2 (video game)