The term 'Cereal Grain Killer' refers to a fungus called ERGOT (5 letters). ERGOT is a fungus that grows on the heads of cereal grains, such as rye, wheat, and barley. It produces alkaloids that can be toxic to humans and animals if ingested. Ingestion of ERGOT can cause a range of symptoms, including hallucinations, convulsions, and even death. ERGOT has been responsible for several epidemics throughout history, most notably the Great Ergotism Epidemic of 994-1001 AD in Europe.