The Guardian of the Threshold is a menacing figure that is described by a number of esoteric teachers. The term "Guardian of the Threshold", often called "dweller on the threshold", indicates a spectral image which is supposed to manifest itself as soon as "the student of the spirit ascends upon the path into the higher worlds of knowledge". The Guardian of the Threshold is also the title of the third play (of a tetralogy of Mystery Dramas) written by Rudolf Steiner in 1912.