In Jewish folklore, a dybbuk is a malicious or benevolent possessing spirit believed to be the dislocated soul of a dead person.
Dybbuks are said to have escaped from Sheol or to have been turned away for serious transgressions, such as suicide, for which the soul is denied entry. The word "dybbuk" is derived from the Hebrew דיבוק, meaning "attachment"; the dybbuk attaches itself to the body of a living person and inhabits the flesh. According to belief, a soul that has been unable to fulfill its function during its lifetime is given another opportunity to do so in dybbuk form. It supposedly leaves the host body once it has accomplished its goal, sometimes after being helped.
There are various origins attributed to these spirits. The earliest description usually hinted that they may be nonhuman demons. Later it was assumed they were the spirits of persons who have died and escaped from Gehenna, a Hebrew term very loosely translated as "hell." The dybbuk may be the soul of a sinner, who wishes to escape the just punishment meted to it by the angels of the grave who seek to beat them, or to avoid another form of soul punishment, which is wandering the earth. Last but not least, it is also considered as a soul that has not been able to fulfill its function in its lifetime is given another opportunity to do so in the form of a dybbuk.
A dybbuk may seek revenge for some evil that was done to it while it lived. Alternatively, it may be lost, and will enter a body simply to seek a rabbi who would be able to help it and send it on its way. The living person may or may not know that a dybbuk is occupying his or her body, or it may be tormented by it. This depends on the intent of the possessing soul.the dybbuk attaches itself to the body of a living person and inhabits it. It will leave once it has accomplished its goal, sometimes after being helped.
Possession: The Dybbuk is said to be able to possess any living or inanimate object. Although the spirit can possess animals, it prefers human hosts. Dybbuk possession may prove to be too much for the unfortunate animal, which may die of "natural causes" or a frantic attemp to drive out the invading spirit shortly afterwards. When the Dybbuk possesses a human, it absolutely refuses to leave. This person may be a total stranger, merely the best and the most convenient host the spirit could find. Legends tell of these spirits inhabiting horses and then jumping into the stable boy.
Fear Inducement: They are also capable of causing someone to feel bone-chilling fear.