Aleister Crowley wrote the Gnostic Mass in 1913, deliberately structuring it on the shape of the Christian Eucharistic liturgy, an entrance, a creed, a consecration, a communion, precisely so that its Thelemic content would sit inside a familiar ecclesiastical frame rather than requiring an unfamiliar new form. Its declared theology replaces the Christian object of worship with a cosmology centered on the individual will and a triad of principal figures, and its officiants include a Priest and Priestess as well as supporting roles, making it a fully staged communal liturgy rather than a private magical working, a public and repeatable rite in a way most of Crowley's other writings are not. Its ecclesiastical trappings, robes, an altar, a consecrated host and wine referred to as Cakes of Light, drew hostile press attention for decades, with newspapers and later popular writers routinely describing it as a black mass or worse despite the text's own explicit distance from that tradition, a confusion helped along by Crowley's own reputation and by his order's secrecy about its other, non liturgical material.
Since Crowley's death in 1947 the rite has continued to be performed by Ordo Templi Orientis bodies internationally, trained clergy conducting it much as originally written, which makes it one of relatively few twentieth century occult compositions still in regular, public, institutionally continuous use rather than surviving only on paper.