2019 Reprint of 1929 Fourth Revided Edition. Full facsimile of the original edition, not reproduced with Optical Recognition software. This pamphlet is a treatise on the denizens of the invisible worlds and the individual's connection with them. Hall discusses Gnomes, Undines, Salamanders, Sylphs, Ghosts, Astral Forms, Specters, Dwellers on the Threshold, The Astral Body, The Building of a Soul, The Passing of the Dweller, The Three Steps and the Sphinx.

Hall was a Canadian-born author, lecturer, astrologer and mystic. He is best known for his 1928 work The Secret Teachings of All Ages. Over his 70-year career, he gave thousands of lectures, including two at Carnegie Hall, and published over 150 volumes. In 1934, he founded The Philosophical Research Society in Los Angeles, which he dedicated to the "Truth Seekers of All Time", with a research library, lecture hall and publishing house. Many of his books are still in print.