Four Horsemen of the Apocalypse, an 1887 painting by Viktor Vasnetsov. From left to right are Death, Famine, War, and Conquest; the Lamb is at the top.
There is no medicine named Delactivine in real life, that Abby uses on Luna and group to treat their Acute Radiation Syndrome (ARS), though the name of disease is real, it is also called radiation sickness or radiation poisoning.