After service with the British Army during the Second World War, he returned to Britain and became the personal secretary of Aleister Crowley, the ceremonial magician who had founded Thelema in 1904.

In 1954 Grant founded the London-based New Isis Lodge, through which he added to many of Crowley's Thelemic teachings, bringing in extraterrestrial themes and influences from the work of fantasy writer H. P. Lovecraft.

During the 1950s he also came to be increasingly interested in Hinduism, exploring the teachings of the Indian guru Ramana Maharshi and publishing a range of articles on the topic.

In 1959 he began publishing on occultism and wrote the Typhonian Trilogies as well as various novels and books of poetry, much of which propagated the work of Crowley and Spare.

Grant's writings and teachings have proved a significant influence over other currents of occultism, including chaos magic, the Temple of Set, and the Dragon Rouge.

[1] By his early teenage years, Grant had read widely on the subject of Western esotericism and Asian religions,[2] including the work of prominent occultist Helena Blavatsky.

[3] He had made use of a personal magical symbol ever since being inspired to do so in a visionary dream he experienced in 1939; he spelled its name variously as A'ashik, Oshik, or Aossic.

Although making some money as an artist and art tutor, he was largely financially supported by his friend Frank Letchford, whom he affectionately referred to as his "son".

Smith was eager to help, and wrote at length on his experiences in founding a lodge, although he was made uneasy by Grant's magical seal of "Aossic" for reasons that have never been ascertained, and their correspondence soon petered out.

[32] In this manifesto, Grant claimed that a new energy was emanating down from Earth from another planet which he identified with Nuit, a goddess who appears in the first chapter of Crowley's Thelemic holy text, The Book of the Law.

[36] During the period in which he worked with the lodge he claimed to have received two important texts from preternatural sources, the Wisdom of S'lba and OKBISh or The Book of the Spider.

[40] He also authored articles on Advaita Vedanta and other Hindu topics for Indian journals like the Bombay-based The Call Divine,[41] as well as for Richard Cavendish's Man, Myth & Magic.

's sex magic teachings needed to be refashioned along tantric principles from Indian religion,[42] in doing so relying heavily on Curwen's ideas about tantra.

[46] Of all OHO contenders, [Grant] made the greatest effort to expand and build upon Crowley's work rather than confine himself to the letter of the law.

(Outer Head of the Order) of O.T.O., claiming that he deserved this title not by direct succession from Crowley but because he displayed the inspiration and innovation that Germer lacked.

[48] A document purportedly by Crowley naming Grant as his successor was subsequently exposed as a hoax created by Robert Taylor, a Typhonian O.T.O.

[52] In 1972, Frederick Muller Limited published the first book in Grant's "Typhonian Trilogies" series, The Magical Revival, in which he discussed various events within the history of Western esotericism while also encouraging future interest in the subject.

[54] This was followed in 1975 by Cults of the Shadow, which brought the first Typhonian Trilogy to an end with a discussion of the left-hand path in magic, making reference to both Crowley and Spare's work, as well as to Voodoo and Tantra.

Encounters with Austin Osman Spare, in which they included 7 years' worth of diary entries, letters, and photographs pertaining to their relationship with the artist.

[68] In his body of work, Grant has created an unlikely mélange comprised of thematic threads that include both Eastern and Western esoteric traditions, in addition to consistent references to artistic and literary works infused with the aroma of the mysterious, fantastic, and uncanny, with a dominant place assigned to the fictional output of H. P. Lovecraft and the visionary creations of Austin O.

[70] Although based in Thelema, Grant's Typhonian tradition has been described as "a bricolage of occultism, Neo-Vedanta, Hindu tantra, Western sexual magic, Surrealism, ufology and Lovecraftian gnosis".

[76] In Central Africa during prehistory, he believed there had been a primordial serpent cult devoted to the worship of a goddess known as Ta-Urt or Typhon, from which the Typhonian tradition stems.

[86] Grant's views on sex magic drew heavily on the importance of sexual dimorphism among humans and the subsequent differentiation of gender roles.

[80] Janine Chapman, an esotericist who met Grant during the 1970s, described him as "an attractive, well-mannered, well-dressed man in his forties, intelligent, cultivated, and friendly.

"[94] The historian of religion Dave Evans noted that Grant was "certainly unique" in the history of British esotericism because of his "close dealings" with Crowley, Spare, and Gardner, the "three most influential Western occultists of the 20th century.

"[95] The occultist and comic book author Alan Moore thought it "hard to name" any other living individual who "has done more to shape contemporary western thinking with regard to Magic" than Grant,[96] and characterized the Typhonian O.T.O.

"[97] In 2003, the historian of Western esotericism Henrik Bogdan expressed the view that Grant was "perhaps (the) most original and prolific English author of the post-modern occultist genre.

[71] The anthropologist Justin Woodman noted that Grant was "one of the key figures" for bringing H. P. Lovecraft's literary works into magical theory and practice,[102] adding that his writings were a "formative influence" on Lovecraftian occult groups like the Esoteric Order of Dagon, founded in North America during the late 1980s.

Here, he asserted that Grant's importance was in attempting to create "a more global character for Thelema" by introducing ideas and concepts borrowed from the Hindu tantra, Yazidism, and Afro-Caribbean syncretic religions.

[95] Evans described Grant as having "an often confusing, oblique, and sanity-challenging writing style" that blends fictional stories with accounts of real-life people.