Phabedes

The planet Phabedes was known for its stable climate and weather patterns held in check by its six moons. The moons, however, served another purpose that was hidden in legend. When positioned in the right alignment, the moons opened up a gateway to a world within the planet. The creatures from the inside of the planet were large ferocious reptilian creatures, with incredible strength. They had webbed feet, red eyes, sharp razor-like teeth and scaly bodies dotted with purple spots. Those that lived on the surface, by contrast, were small, thin, blue-skinned and humanoid in appearance with purple hair.

When the solution to the puzzle of the alignment of the moons was forgotten, and terrible storms were unleashed on the planet below due to the disruption of the moons, the Eleventh Doctor provided the solution, drawn on a paper dart. (COMIC: Eye of the Storm)