Catherine Monvoisin, or Montvoisin, née Deshayes, known as "La Voisin" (c. 1640 – February 22, 1680), was a French fortune teller, poisoner, and an alleged sorceress, one of the chief personages in the affaire des poisons, during the reign of Louis XIV. Her purported cult (Affair of the Poisons) was suspected to have killed anywhere between 1000-2500 people in Black Masses. Catherine Deshayes was married to Antoine Monvoisin, a jeweller with a shop at Pont-Marie in Paris. After her husband was...