Death cap mushrooms are highly toxic fungi known scientifically as Amanita phalloides. They are responsible for the majority of mushroom poisoning deaths worldwide. These mushrooms typically have a greenish or yellowish cap and a white stem, making them resemble some edible varieties. Consuming even a small amount of a death cap can lead to severe liver and kidney damage. Symptoms may not appear until 6 to 12 hours after ingestion, often leading to a false sense of security. It is crucial to avoid foraging for wild mushrooms unless you are an expert, as misidentification can be deadly.