What is a mullaskus?

It seems there might be a typo in your question, as "mullaskus" doesn't correspond to any known term. If you meant "mollusk," then mollusks are a diverse group of invertebrates that include animals such as snails, clams, and octopuses. They are characterized by soft bodies, often protected by a hard shell, and play important roles in marine and terrestrial ecosystems. If you meant something else, please clarify!