Ergot

Ergot is a poisonous fungus that can infect the cereal crops of rye, barley and wheat. Humidity and cool weather together with a late harvest favour its propagation. Ergot is not readily identifiable when ground up together with rye grain given its reddish colour, making rye flour the principle delivery vector for the substance. It is a potent hallucinogen, which can cause permanent mental impairment. It also causes convulsions and is capable of killing through localised necrosis, typically in the extremities.