Joris-Karl Huysmans, “J.K.” for the friends, had been a naturalist writer and then wrote the “bible” of decadence (”A rebours”/”Against Nature”). If you want to read all about his early years, take a look here:
Now, at the age of 42, J.K. was at a turning point in his life and his career. In 1890 he wrote to the young Dutch novelist Arie Prins that he was looking for “a demoniac sodomite priest” who performed the black mass. J.K. needed him for a new book. He had to insinuate himself into the word of the occultists for what would become “Là-bas” (translated as “Down There” in 1924, and “The Damned”).
Huysmans made contact with Berthe Courrière, thanks to her lover, the writer Remy de Gourmont. Berthe believed in black magic and beguiled J.K. with tales of her paranormal experiences. Huysmans also had a brief and bizarre affair with another Lady of the Occult, Henriette Maillat. Both she and Berthe were the models for Hyacinthe Chantelouve, the heroine “down there”.
Huysmans contacted, among others, a founding member of the modern French Order of the Rosy Cross, Stanislas de Guaïta; a self-proclaimed descendant of the Chaldean Magi, Sâr Joséphin Péladan; an expert on alchemy, Michel de Lézinier; the renegade priest and exquisitely evil Joseph-Antoine Boullan, no stranger of prisons, who regarded all forms of sexual intercourse as acts of worship and who was accused of having slain his own child, conceived by a nun, on the altar, after a Black Mass. Boullan provided Huysmans with all sorts of documentation on the black arts in 19th century France.