The Nedenah are short, bluish-grey-skinned humanoids with slender limbs and elliptical green or blue eyes, which travel through space in flying saucers. Their blood is brownish yellow in color. Although they have been known to visit Earth for thousands of years, their visitations are purely for scientific observation and they primarily avoid contaminating human culture. Unfortunately, in 1947 one of their ships crashed in Roswell, New Mexico and the inhabitants were forcefully brought to Area 51, where the USA military has been studying their technology ever since. They are described as old enemies of the Waro and are also in war against the Viperox.
This species first appeared in the 1997 Doctor Who novel The Devil Goblins from Neptune, by Heith Topping and Martin Day; featuring the Third Doctor. They later appeared unnamed in the 2009 animated special Dreamland, featuring the Tenth Doctor. Despite some facts which prevent the two stories from taking place in the same continuity (there are inconsistencies regarding the number of aliens present in the Roswell crash, as well as the circumstances of said crash) it is very clear that the creatures are meant to represent the same species.