The Dweller on the Threshold is an entity we encounter in both Theosophy and the Arcane School of Alice A. Bailey. Below are some quotes on the Dweller on the Threshold in the writings of Alice A. Bailey(AAB) and Djwhal Khul (DK). Links on these pages are to the online books at the Lucis Trust website.
In Scorpio, two most occult factors emerge from the past and begin to engross the attention of the disciple. One is memory and the other is, as a consequence of the memory, the Dweller on the Threshold. Memory in the sense here involved is not simply just a faculty of the mind, as is so oft supposed, but it is essentially a creative power.
It is basically an aspect of thought and—coupled with imagination—is a creative agent because thoughts are things, as well you know. From ancient recesses of the memory, from a deeply rooted past which is definitely recalled, and from the racial and the individual subconscious (or founded and established thought reservoirs and desires, inherited and inherent) there emerges from individual past lives and experience that which is the sum total of all instinctual tendencies, of all inherited glamours and of all phases of wrong mental attitudes; to these (as they constitute a blended whole) we give the name of the Dweller on the Threshold. This Dweller is the sum total of all the personality characteristics which have remained unconquered and unsubdued and which must be finally overcome before initiation can be taken.
Each life sees some progress made; some personality defects straightened out and some real advance effected. But the unconquered residue and the ancient liabilities are numerous and excessively potent and—when soul contact is adequately established—there eventuates a life wherein the highly developed and powerful personality becomes, in itself, the Dweller on the Threshold. Then the Angel of the Presence and the Dweller stand face to face and something must then be done.
Upon the mental plane the Angel of the Presence and the Dweller on the Threshold are brought face to face. Their synthesis is brought about upon the Path of Initiation.
The analogy can also be carried forward onto the mental plane and when the energies of the sun sign and the rising sign are coherently blended and expressed (in the case of both the individual or a planetary Life) there comes a point of crisis wherein the soul and the personality are brought face to face. The Angel of the Presence, distributing solar fire and holding focussed electric fire, and the Dweller on the Threshold, expressing and utilising fire by friction, know each other “with intimate occult knowledge. ” The door then stands open wide through which the life and light of the three major constellations can—after the third initiation—be occultly available to the initiate, be he a liberated human being or a planetary Logos.