The term 'Bane of Cereal Grain' can be summarized as a reference to ERGOT, a five-letter fungus that infects cereal grains and can cause serious health problems. ERGOT is a type of fungus that grows on the heads of cereal grains such as rye, wheat, and barley, and produces toxins that can cause hallucinations, convulsions, and even death if ingested. It is a major problem for farmers, as it can reduce crop yields and contaminate food supplies.