In 1667, he officiated, alongside abbé Mariette in a black mass, arranged by La Voisin for the royal mistress Madame de Montespan, where she asked for the king to love her by the help of Satan.
The same year, Lesage was condemned to the galleys for having participated in black masses; he was freed in 1672 by the connections of La Voisin and resumed his position in her organisation.
In July-August 1680, after the execution of La Voisin on 22 February, her daughter Marguerite Monvoisin, made a full confession, revealing the client list of her mother, which included the king's mistress Madame de Montespan, and the aphrodisiacs, black masses and murder of the king ordered by Montespan.
In November, Montespan was further implicated when her chamber lady, Claude de Vin des Œillets, was identified by the prisoners.
Adam Lesage, Étienne Guibourg, Marguerite Monvoisin and a number of others involved were never brought to trial, which would have made their testimonies public.
Louvois recommended that he be put on water and bread and beaten day and night to make him talk, but that he was a habitual liar.