[1] Her background was upper middle-class;[2] the Firths were a wealthy English family who had gained their money through the steel industry in Sheffield, Yorkshire, where they had specialised in the production of guns.

[3] Fortune's paternal grandfather John Firth had devised a family motto, "Deo, non Fortuna" ("God, not Luck"), to mark out their nouveau riche status; she would later make use of it in creating her pseudonym.

[7] Sarah was keenly interested in Christian Science,[8] and Gareth Knight notes that both of Firth's parents were active practitioners of the religion,[9] while fellow biographer Alan Richardson expresses doubt that there was sufficient evidence as to the seriousness with which Fortune herself regarded it.

But I had considerable experience of practical occultism before I made its acquaintance, and I immediately recognised power of a degree and kind I had never met before, and had not the slightest doubt but that I was on the trail of the genuine tradition, despite its inadequate exposition."

[40] Fortune became an acolyte of Moriarty's Masonic-influenced lodge, which was based in Hammersmith,[41] and joined his community of followers living at Gwen Stafford-Allen's home in Bishop's Stortford.

[45] In tandem with her studies under Moriarty, in 1919 Fortune had been initiated into the London Temple of the Alpha et Omega, an occult group that had developed from the Hermetic Order of the Golden Dawn.

[48] She was not enamoured with the ceremonial magic system that had been developed by the Golden Dawn,[49] however it did provide her with the grounding in the study of the Hermetic Qabalah which would exert a great influence over her esoteric world-view.

Along with an anonymous woman known only as "E. P.", the pair carried out acts of trance mediumship, claiming that in doing so they entered into psychic contact with the Ascended Masters; Fortune later identified these as Socrates, Thomas Erskine, and a young military officer named David Carstairs who had died at the Battle of Ypres.

[85] When Jiddu Krishnamurti abandoned Theosophy, causing problems for the Theosophical movement, Fortune endorsed the 'Back to Blavatsky' faction, attacking Leadbeater in print by accusing him of being a practitioner of black magic.

[112] In late 1931, Fortune began mooting the idea of the construction of a permanent base, or Sanctuary, at the Chalice Orchard, and despite the economic obstacles of the Great Depression was able to raise sufficient funds.

[113] The group experienced a growth in the numbers attending its lectures, subscribing to its correspondence course, and using their private library; conversely, their Sunday services were not very popular, with a move from the morning to the evening seeing no effect.

[132] The work constituted a theoretical discussion based in the Golden Dawn system of correspondences to the Qabalic Tree of Life which she had obtained through her membership of the Alpha et Omega group.

[134] Her final novel, Moon Magic, was apparently left unfinished prior to the outbreak of the Second World War; a protégé later completed it, claiming to have done so through channeling Blavatsky's disembodied spirit, and it was published posthumously.

[143] She urged Fraternity members to repeat a mantra every time the German Luftwaffe began bombing Britain, through which she hoped to call upon "Invisible Helpers" from the "Inner Planes" to aid the people affected.

[146] After the United States entered the conflict in December 1941, Fortune began assembling plans for the post-war period, believing it would mark the dawning of the Age of Aquarius.

[153] In August 1940, Fortune embarked on a further project of trance mediumship, this time with her Alpha et Omega mentor, Curtis-Webb (now renamed Maiya Tranchall-Hayes), in the hope of contacting the same Masters who they believed had aided the Hermetic Order of the Golden Dawn.

[156] The claims produced in these channelled meditations presented the Arthurian myths as racial memories that had been passed down from Atlantis, having been brought to Britain by Atlantean settlers after the cataclysm that destroyed their island.

[161] During Fortune's lifetime, some of the Fraternity members had expressed concerns with regard to the organisation becoming a personality cult revolving around her, and so following her death they did not encourage an interest in her biography.

The literary scholar Susan Johnson Graf categorises these alongside the work of H. Rider Haggard, Algernon Blackwood, Charles Williams, and Arthur Machen.

[170] Fortune's first novel was The Demon Lover, which tells the story of Veronica Mainwaring, a young virgin woman who becomes the secretary to a malevolent magician, Justin Lucas, who seeks to exploit her latent mediumistic powers for his own purposes.

He meets with Le Fay Morgan, a spiritual adept, and together they enter an obsessive (on Wilfred's part) but platonic relationship while establishing a temple to the sea gods.

Above all she was a deft synthesizer of ideas, and her continued influence derives largely from her ability to bring difficult esoteric concepts into a lucid and readily accessible prose."

[197] Nevertheless, she believed that particular spiritual traditions were allotted to specific racial groups,[187] stating that "the Great White Lodge gives to each race the religion suited to its needs".

[204] The magical principles on which her Fraternity was based were adopted from the late nineteenth century Hermetic Order of the Golden Dawn, with other influences coming from Theosophy and Christian Science.

[233] Hutton nevertheless considered her to be the "foremost female figure" of early 20th century British occultism,[186] while historian Alex Owen referred to her as "one of the most significant clairvoyants and occultists of the postwar period".

[186] Richardson's book relied heavily on the recollections of Christine Hartley,[249] while the publication of Fielding and Carr was based upon the authors' interactions with older members of the Society.

[165] In the early 21st century, Evans noted that Fortune's work was "still influential in some magical quarters",[217] highlighting that in his experience she was one of only three female ceremonial magicians—alongside Leah Hirsig and Jaq Hawkins—that modern esotericists could readily name.

The religious studies scholar Hugh Urban noted that Fortune was "one of the key links" between early twentieth-century ceremonial magic and the developing Pagan religion of Wicca.

[191] The religious studies scholar Graham Harvey compared The Sea Priestess to the Wiccan Gerald Gardner's 1949 novel High Magic's Aid, stating that while neither were "great literature", they "evoke Paganism better than later more didactic works".

[96] Evans nevertheless believed that her writings were "stuck in their era" in many places; as evidence, he highlighted passages in which Fortune warns her readers that their Indian servants may steal their body waste products for use in the worship of the Hindu goddess Kali.