Wiedergänger

They exist either to avenge some injustice they experienced while alive, or because their soul is not ready to be released, as a consequence of their former way of life.

In different parts of Germany, until the early 20th century, the belief was common that dead ones lived on, after their death, and exerted a disastrous influence from the grave.

This influence was believed to be partly done via a telepathic effect (sympathy charm), so that the nachzehrer, as the villain was called, did not need to rise from the grave and still could suck the vitality from living persons with his open mouth, his open eye and by gnawing on the burial shroud.

The aufhocker (also called "huckop" or "huckupp") became ever more heavy, and the victim would finally break down exhausted or dead.

These generally describe a revenant in the broad sense, but can by extension also refer to regular ghosts and visitors from the afterlife etc.