A Ghost (sometimes known as a Spirit or a Soul) is the spirit of a deceased individual who haunts the area of their death, normally as the result of a violent or untimely death - usually Ghosts are considered frightening but otherwise harmless but there are numerous accounts of more violent encounters with ghosts in folklore, some of the more extreme examples were found in phenomena that has now become known as Poltergeists' activity.
The idea of the dead rising from the grave is as old as death itself and unlike the revenant or vampire the ghost has always been considered a spiritual threat rather than a physical one and often they haunt people or warn them of dangers, sometimes a ghost will seek revenge on those responsible for its demise or will try to force someone into aiding it find rest.
Ghosts may at times become violent and cruel, though when a ghost becomes exceptionally dangerous it is more accurately described as a type of Demon - especially if it begins to possess the living.
Although most ghosts take the form of humans there are tales of ghostly animals and even more unusual sightings such as trains, cars or ships.
Notable Hostile Ghosts
A poltergeist is a noisy spirit, often invisible and known for hurling objects across rooms or creating banging noises to disturb residents of their domain. Poltergeists may also be violent, pulling people's hair, clawing at them and even (in some stories) killing them: the difference between a poltergeist and a ghost is a controversial one with some viewing them as the same while some view poltergeists as a byproduct of psychic energy, akin to a thought-form (what Buddhists referred to as Tulpas).
Extremely violent and/or disturbing poltergeists can be considered demons or undead spirits by many and although it is not often performed in the modern world there are various exorcism rites in most religions dealing with ways to get rid of dangerous or unwanted spirits - many of which manifest poltergeist activity.
In the books of Harry Potter, Peeves the Poltergeist have made poltergeists more known to the public at large, as he is the typical poltergeist character: sadistic, annoying, troublemaking and violent. The author J.K Rowling has described Peeves as "an indestructible spirit of chaos".
The Wild Hunt (from an ancient European myth) are spectral group of hunters, horses and hounds, rampaging in violent pursuit across the sky and on the ground, or floating somewhere in between. Witnessing the Wild Hunt is thought to be an omen of death, war, plague, or other catastrophe. Occasionally the participants in the hunt are included to have faeries, gods, or ancient heroes, but traditionally wild hunters are strongly composed of the dead: lost souls, spirits, and ghosts.
Vetala (from Hindu folklore) are spirits who tend to haunt places of burial and crypts; trapped between life and the afterlife, they can take possession of corpses and stir up all kinds of trouble for the living.
La Llorona (from Spanish and Mexican legends) aka The Weeping Woman, is a spirit who killed her own children by drowning in order to be with her lover, only to be rejected by him and driven mad, committed suicide. Constantly crying, La Llorona is cursed to search for her dead children in futility for eternity, sometimes attempting to steal living children.
Jima (from Amazonian folklore) are Feared specters by the Wari, an Amazonian rainforest tribe. Jima are known for grabbing their living victims with their incredibly strong and extremely poisonous hands, all the while attempting to tear the victim’s spirit away from body.