Guardians of the threshold:
https://en.wikipedia.org/wiki/Guardian_of_the_Threshold
The Guardian of the Threshold is a menacing figure that is described by a number of esoteric teachers.[1][2][3][4] 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".[5][6][7] 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.