Claviceps purpurea is a fungus that primarily infects rye and other grasses. It produces dark, elongated structures called sclerotia, which replace the grain in the host plant. These sclerotia can be harvested and have historically been used in traditional medicine. The fungus is known for producing alkaloids, which can be toxic to humans and animals if ingested. Consumption of contaminated grain can lead to a condition known as ergotism, characterized by symptoms such as hallucinations, convulsions, and gangrene. Despite its dangers, some compounds derived from Claviceps purpurea are used in modern medicine, particularly in treating migraines.