There are two subcategories of clods: "mother" and "father" clods. Mothers are large, stationary slagic organisms that produce new slagic organisms by encapsulating non-slagic creatures in cocoons.
Extremely varied in appearance and ability, mutations are defined as non-slagic creatures who have been infected and have begun morphing but have not yet taken a final form (such as a clod or runner).
Slag is the slang term used to describe the alien organism Boletus Mortiferum, often referred to as "the fungus", "the virus", or "krozox". The origins of slag are yet unknown, though it is believed to have originated from far beyond the solar system of Earth.