The Psionovores were energy-based beings inhabiting the ionised dust left by comets in interstellar space. Under normal conditions they could shape the dust into a semblance of solid objects, but maintaining those objects took significant will. With enough channelled will power, any manner of objects could be created wherever they wished, and could interact with other physical objects. Bad thoughts and desires were food for Psionovores. The Eighth Doctor described it this way: