This book, the first of its kind in English, examines an initiatic society known by various names—Illuminés d’Avignon, the Avignon Society, the Union, the New Israel Society—that flourished in Berlin, Avignon, Rome, and St. Petersburg, between 1779 and 1807. The founding members of this society forged a group that embraced strands of Western esotericism (particularly alchemy and arithmancy) within an all-pervading millenarian worldview. Whilst the society incorporated aspects of high-degree Freemasonry, it was never merely a para-masonic fraternity. Instead, it offered entry into a religious community of the elect for men, women, and children who anticipated the imminent onset of the millennium. Consecrates were also able to seek divine advice from the so-called Holy Word, partake in alchemical operations to perfect the philosophers’ stone, and invoke guardian angels. As this study demonstrates, the group retained its millenarian worldview and belief in prophetic mediation with Heaven throughout its existence. But it also experienced pronounced doctrinal shifts. Notably, the early espousal of Swedenborgianism was jettisoned in late 1788 and replaced by an embrace of Marianism. This change reflected a contested turn away from a more ecumenical outlook to a more conventional Catholic society. Further, although the society ceased to function in 1807, this study examines the enduring legacy of the group in Russia and its direct influence on Emperor Alexander through the prophetess Madame Bouche, who spent two years at the imperial court (1819 to 1821). It draws on a wealth of archival material from across Europe, which reflects the pan-European composition of the society itself.