Mithridates VI grew up in the Hellenistic kingdom of Pontus on the Black Sea, where his father, Mithridates V, was poisoned by his own attendants. With his mother ruling as regent and favoring his brother, the young prince suffered persistent stomach pains after meals and concluded that she was slowly poisoning his food. He fled into the wilderness and, guided by Scythian shamans known as the Agari, began swallowing small doses of local poisons such as aconite, hemlock and snake venom, hoping to make his body immune to every toxin. He returned to take the throne and became a persistent enemy of Rome, and the practice took his name: mithridatism.

Roman physicians claimed to have his formula, called mithridatium, and spent generations adding ingredients to it. The episode follows the idea to Rasputin’s survival of cyanide cakes, a theory the hosts call debated, and to the Mauryan Empire, where the Vishakanyas, or poison maidens, were said to be raised on poison until their bodies became lethal, and where Chanakya’s secret dosing of Emperor Chandragupta led to the death of Queen Durdhara and the birth of Bindusara. It then explains, as the transcript states, why the body can build antibodies to complex venoms but only metabolic tolerance, through liver enzymes, to chemicals, and why heavy metals and large cyanide doses defeat the strategy.

• The liver as a nightclub bouncer that learns to eject regular troublemakers but cannot stop a wrecking ball
• Rhodanese, the enzyme that turns small amounts of cyanide into thiocyanate, and the sulfur limit that caps it
• A drop of the dying queen’s poisoned blood on the infant’s forehead, the blue bindu that named Bindusara
• Mithridatism in The Count of Monte Cristo, Rappaccini’s Daughter, Strong Poison and The Princess Bride
• A.E. Housman’s use of the legend in A Shropshire Lad to defend reading dark, serious poetry