In 1679, Madame de Montespan commissioned La Voisin to murder King Louis XIV of France.
As a friend, Trianon tried to convince La Voisin to abandon the plan, even making up a horoscope to warn her that it would be a mistake, but did not succeed.
Upon her arrest, authorities found 25 "manuscript volumes on the occult sciences" in her house.
[2] In August 1680, after the execution of La Voisin in February, the connection between La Voisin, Montespan, and the plan to assassinate the King was revealed by her daughter, Marguerite Monvoisin, who on 9 October also confirmed the statements made by Adam Lesage in August of child sacrifice at the black masses.
Catherine Trianon is given a fairly large portrayal in a novel by Judith Merkle Riley: The Oracle Glass (1994)