The Medusoid Mycelium, also known as the Mycelium is a deadly mushroom and an evil phenomenon found in the novel series A Series of Unfortunate Events. It is a highly contagious, dangerous black coloured mushroom which lives in aquatic environments or in damp places. When infecting a human, it enters through the mouth or eyes. One single spore can kill an entire person in an hour, unless the victim takes the only known cure - horseradish. Ishmael was prepared for such an outbreak, and he made use of the horseradish-coated apples in his arboterum to protect himself.