Fuller had an occultist side that oddly mixed with his military side. He was an early disciple of English poet and magician Aleister Crowley, and was very familiar with his and other forms of magick and mysticism. While serving in the First Oxfordshire Light Infantry he had entered and won a contest to write the best review of Crowley's poetic works, after which it turned out that he was the only entrant. This essay was later published in book form in 1907 as "The Star in the West". After this he became an enthusiastic supporter of Crowley, joining his magical order, the A∴A∴., within which he became a leading member, editing order documents and its journal, "The Equinox". During this period he wrote "The Treasure House of Images", edited early sections of Crowley's magical autobiography "The Temple of Solomon the King" and produced highly regarded paintings dealing with A∴A∴ teachings: these paintings have been used in recent years as the covers of the journal's revival, "The Equinox, Volume IV".