Häxan it's a cult movie directed in 1922 by Benjamin Christensen. At that time instantly achieved the attention of the surrealists and then of many artists interested in occult.
Based on a german manual for inquisitors from XV century, the movie presents a series of macabre medieval imaginaries composed of devil's worshipers, torturers, grave robbers, possessed and Satan himself, interpreted by the director.
A mix between mockumentary and horror movie, not without black humour, the movie follows the history of witchcraft and explores the scientific hypothesis that the medieval time witches suffered of the same hysteria of the psychiatric patients of contemporary times. 
The movie alternates sequences of documentary slant - the diabolic iconography, the different types of sorcery, the relationship between witchcraft and hysteria - with episodes based mainly on dramatic action.
At silent movies' times the censorship saved some meters of film, at least in north Europe.
A movie of great importance in movies' history for many aspects like the wise use, innovative at that times, of close-up, makes no concessions to anyone and the witches' sabbath can happen with philologic accuracy.
Everything combined with the double bass, guembri (instrument connected with Gnawa music and possession rites) and the electronic processing by Antonio Bertoni. The music played live it's a mixture of composition, improvisation, electronic layering and ethnic music, covering together  with the movie's images centuries of obscure sonorities.