The Parasites that lived on the shell of a giant space turtle the (Terrapratch), were large purple creatures armed with weapon sticks, that lived a somewhat primitive existence unaware of their environment. Their use of drills to extract a white fatty substance from ‘underground’ for both building and feeding purposes was harming the creature beneath. They believed a series of earthquakes to be the displeasure of the Great Sky Goblins demanding sacrifice in a temple built to honour them at The Edge of The World. The Doctor took photographs from above the planet from the TARDIS to prove to the creatures that they lived a parasitic existence resulting in a greater respect for the Terrapratch that they were so dependant on. (COMIC: The Parasites)