A VAMPIRIC WITCH well versed in the black arts, from the folklore of Austria and Bavaria, the drude has been reported as far back as the twelfth century. Almost always a woman, it will shapeshift into a bird at night and seek out a man, as they are powerless against her, to inflict horrible nightmares and terrible visions upon. She can be warded off with a drudenstein (“drude’s stone”), a stone with a naturally occurring hole in it, or with a drudenkreuz (“drude’s cross”), essentially a pentagram.

Source: Grimm, Teutonic Mythology, 1041; Jones, On the Nightmare, 218; Pearson, Chances of Death, 181