Maybe you could tell us something about basilisks?
A basilisk’s aura rots vegetation, covers soil with mildew, turns water into poisonous broth, and changes air into corrosive gas, killing every animal in the vicinity. Areas thus afflicted become toxic pits that remain deadly for weeks. Nothing grows in these wastelands for months afterwards, and anyone unfortunate enough to find themselves in the area (or too foolish to avoid it) suffers nausea, headaches, blurred vision, and even blindness.
