Ink.
Have you heard of Aqua Tofana? The dark story of the potion from real Italian history has long beguiled, as it’s a true story of feminine (and some say darkly feminist) mass poisoning! A 17th century black widow secret society, wielding an arsenic-based poison, sold by 3 generations of murderous bitches, successfully killed around 600, mostly disfavored husbands. Has any other female(s) slain so many? The toxin was sold in innocuous cosmetics containers or as Manna di San Nicola, aka Santa Claus.