Hirsig was born into a family of nine siblings in Trachselwald, Canton of Bern, Switzerland. However, they moved to the United States when she was a child aged two, and she grew up in New York City. Growing up in the city, she was taught at a high school in the Bronx.
She and her older sister Alma were drawn to the study of the occult, and this interest led them in the spring of 1918 to pay a visit to Aleister Crowley, who was living at the time in the Greenwich Village neighborhood of Manhattan. Crowley and Hirsig felt an immediate and instinctive connection. Leah asked him to paint her as a "dead soul" and in fact Crowley painted several portraits of her.
In 1919, after seeking out Aleister Crowley due to her interest in the occult, she was consecrated as his Babalon or, "Scarlet Woman", taking the name Alostrael, "the womb (or grail) of God." Leah Hirsig wrote in her 1921 diary: "I dedicate myself wholly to The Great Work. I will work for wickedness, I will kill my heart, I will be shameless before all men, I will freely prostitute my body to all creatures".
Leah had previously been married to Edward Hammond, by whom she had a son, Hans Hammond (13 Nov 1917-Oct 1985).
Soon after moving from West 9th St. in Greenwich Village New York City with their newborn daughter Anne Leah nicknamed Poupée, Crowley, along with Leah Hirsig, founded the Abbey of Thelema in Cefalù (Palermo), Sicily on 14 April 1920, the day the lease for the villa Santa Barbara was signed by Sir Alastor de Kerval (Crowley) and Contessa Lea Harcourt (Leah Hirsig). The Crowleys arrived in Cefalu on 1 April 1920. During their stay at the abbey, Ms Hirsig was known as Soror Alostrael, Crowley's Scarlet Woman, the name Crowley used for his female sex magick practitioners in reference to the consort of the Beast of the Apocalypse whose number is 666.
Of her time there, Frater Hippokleides (2003) writes:
At the Abbey, Hirsig was instrumental in guiding Crowley, the Prophet of the New Aeon, to a deeper understanding of the Law of Thelema. At a time of despair, Crowley wrote, "What really pulled me from the pit was the courage, wisdom, understanding and divine enlightenment of the Ape herself. Over and over again, she smote into my soul that I must understand the way of the gods ... We must not look to the dead past, or gamble with the unformed future; we must live wholly in the present, wholly absorbed in the Great Work, 'unassuaged of purpose, delivered from the lust of result'. Only so could will be pure and perfect."
Crowley wrote one of his most confronting poems, "Leah Sublime" (which has been called "alarmingly obscene"), in her honour. In Leah, Crowley found an ideal magical partner. He called her vagina "the Hirsig patent vacuum-pump".
After Raoul Loveday died from drinking contaminated water at Cefalù, Mary Butts reported in one of her journals about Hirsig of an unsuccessful attempt to induce a he-goat to copulate with her at the Abbey of Thelema, emulating an ancient pagan ritual (an account corroborated by Crowley himself in an unpublished passage in one of his diaries).
With Crowley, Leah had a daughter, whom they named Anna Leah (Poupée) Crowley. She was born on 26 Jan 1920 in Fontainebleau, France. She died on 15 Oct 1920.
Hirsig's role as Crowley's initiatrix reached a pinnacle in the spring of 1921 when she presided over his attainment of the grade of Ipsissimus, the only witness to the event.
By June 1924, while Hirsig—the Scarlet Woman—stayed loyal to Crowley during money troubles and painful surgeries for his asthma symptoms, the two of them found their relationship was suffering. She wrote in her diary that his "rasping voice so jarred me that I wanted to scream." After a few months Crowley broke it off, presenting her with a new "Scarlet Woman" by the name of Dorothy Olsen.
But this did not lead Hirsig to abandon her commitment to Thelema. Her diary from this period reveals her continuing devotion to the Great Work, her renewal of her magical oaths, her ongoing invocations of Ra Hoor Khuit, and her consecration of herself as the bride of Chaos. In 1925, when Crowley asked her to serve again for a period as his scribe and secretary, she readily accepted; she was ready to give her assistance when it was necessary to the furtherance of his magical work and to the promulgation of the Law of Thelema. As Crowley wrote in his diary during the Cefalù period, "She loves me for my work ... She knows and loves the God in me, not the man; and therefore she has conquered the great enemy that hides behind his clouds of poisonous gas, Illusion."
Hirsig spent the winter in Paris, France, where her financial problems continued. Crowley biographer Lawrence Sutin rejects the assertion of earlier writers that she worked as a prostitute. She continued to work for Crowley and the promulgation of Thelema for at least three years.
She later married William George Barron, with whom she had a son, Alexander Barron (4 Dec 1925-?)
On March 13, 1926 her sister Marian Dockerill, born Anna Maria Hirsig, published her exposé on Aleister Crowley, on 'Oom the Omnipotent' Pierre Bernard (yogi) and others in a series of articles which began running on this date in the New York Journal, titled "My Life in a Love Cult, A Warning to All Young Girls". This exposé has been adjudicated -incorrectly- to their other sister Magdalena Alma Hirsig, in the belief that Marian Dockerill was not a real name, but a pseudonym.
Hirsig later rejected Crowley's status as a prophet, while still recognizing the Law of Thelema. Ultimately she returned to her work as a schoolteacher in America. John Symonds, "Crowley's most hostile biographer," claimed to find rumors of her converting to Roman Catholicism.
Hirsig died in 1975 in Meiringen, Switzerland, aged 91.
In popular culture
- She was the namesake of the 1989 song "Leah Hirsig", by San Francisco rock band The Ophelias, in which she is described in the chorus as "sweet mother of the living light"
- Marta Timon portrayed her in the 2003 Carlos Atanes film Perdurabo
- She is an aspect of the god of the 3rd Sphere in Alan Moore's Promethea series (2003)
- The role of Leah Hirsig was played by Natalie Hughes in the 2007 Robert Garofalo documentary film In Search of the Great Beast 666
- Lynn Mastio Rice portrayed her in the 2007 Vincent Jennings film Abbey of Thelema
- She appears as a vampire and the true form of the mandrill Aiwass in the French comic Requiem Chevalier Vampire
- John Symonds, in introduction, page ix, to Aleister Crowley, White Stains (London, Duckworth, 1986); cited by Richard Kaczinsky, Perdurabo: The Life of Aleister Crowley (North Atlantic Books, 2010). ISBN 978-1-55643-899-8
- Sutin, p318,319
- Sutin p321, 322.
- Sutin, p330.
- Robert Anton Wilson, compiled remarks from Paul Krassner's The Realist, issues 91-B, C, 92-A, B (1971-2)
- similar statement by Justin Scott Van Kleeck, The Art of the Law, available from http://www.esoteric.msu.edu/VolumeV/ArtofLaw.htm Sept 2, 2008
- via Sutin, p330.
- Hirsig, Leah. The Magical Record of the Scarlet Woman. 
- Lawrence Sutin, Do What Thou Wilt: A Life of Aleister Crowley. St. Martin's Griffin, New York 2000.
- Thelemapedia. (2004). Leah Hirsig. Retrieved April 28, 2006.
- Frater Hippokleides. (2003). Leah Hirsig.
- Leah Hirsig art and photos at Picasaweb