Poltergeist

"The name 'poltergeist' is German in origin, and roughly translates as 'noisy ghost', although it is not, strictly speaking, a ghost at all. The poltergeist is an invisible entity that moves objects, slams doors and creates other audible, kinetic disturbances. It has been reported in many cultures and there is a strong association with the places where young people, especially adolescents, are living. Explanations for the phenomenon vary all the way from supernatural to scientific."

- Description.

A poltergeist is an "indestructible spirit of chaos." . They haunt one specific location at time, generally those inhabited by a large number of adolescents, and either "[came] with the building," or chose to enter it at some point. They are among the creatures classed as non-beings.

Poltergeists generally do not have a physical form, with one notable exception being Peeves, the poltergeist that haunts Hogwarts Castle.

Abilities
Poltergeists can fly and delight in vandalism, malicious mischief, and the general aggravation and embarrassment of living persons. They could unscrew chandeliers, write rude words on chalkboards, throw water balloons at people, throw walking sticks at people, stuff keyholes with chewing gum and other such acts, simply for their amusement.

Behaviour
Poltergeists are notably unruly - there was no way to get rid of a poltergeist once it had moved into a location. Some people could get it to settle down for a while, though it would inevitably start acting up again. Dolores Umbridge claimed that the Minister of Magic could sign an order banning a poltergeist, and once threatened Peeves with this action. However, her statement may reflect her belief in the superiority of wizards in general and the Ministry of Magic in particular, rather than specific knowledge of the nature of poltergeists, and that her efforts would be wasted.

Comparison to ghosts
Whilst similar, poltergeists differ from ghosts in a number of ways. Firstly, ghosts are incorporeal, whereas the poltergeist, despite not normally having a physical form, is solid enough to move objects with physical force. Poltergeists have never once been living humans either. The latter trait may indicate amortality, the condition of never having died and being unable to die, as one was never alive to start. Poltergeists with form have enough physicality that they can have gum fly up their noses, and they are vulnerable to some of the same hexes as humans, including Langlock.

Known Poltergeists

 * Handsome Poltergeist
 * Peeves

Etymology
"Poltergeist" comes from the German, poltern, meaning "to make (loud) noise" and geist, meaning "ghost" or "spirit." The German plural form is "Poltergeister."

Behind the scenes

 * It may be possible that poltergeists form from (and consequently feed on) the chaos of an area. If so then it may also be possible that - if their home were to be left desolate for long enough - a poltergeist would not die but simply cease to exist, at least until the locale became more active again.
 * Fleur Delacour once stated that if a poltergeist was ever discovered in the Palace of Beauxbatons, it would be immediately expelled. This is impossible, however, as J. K. Rowling has stated a poltergeist cannot be driven by any means, from a location it has decided to haunt. As such, Dolores Umbridge's request to Cornelius Fudge to sign an Order for the Expulsion of Peeves from Hogwarts was also a complete waste of effort on her part.

Appearances

 * Harry Potter and the Philosopher's Stone
 * Harry Potter and the Philosopher's Stone (film)
 * Harry Potter and the Philosopher's Stone (video game)
 * Harry Potter and the Chamber of Secrets
 * Harry Potter and the Chamber of Secrets (video game)
 * Harry Potter and the Prisoner of Azkaban
 * Harry Potter and the Prisoner of Azkaban (video game)
 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Order of the Phoenix (video game)
 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Deathly Hallows
 * LEGO Harry Potter: Building the Magical World
 * LEGO Harry Potter: Characters of the Magical World
 * The Queen's Handbag
 * LEGO Harry Potter: Years 1-4 
 * Harry Potter LEGO Sets
 * Pottermore