Nimon

The Nimons are a sapient nomadic species. They travel from planet to planet consuming entire populations and resources, and refer to this as the Great Journey of Life.

Biology
The Nimons are quasi-humanoid creatures with black skin, over-sized heads and no necks. Their eyes are brightly red and they have no visible mouth. A pair of long, conical horns protrudes from their heads, from which they can shoot energy discharges. According to Romana, the Nimons feed on the "binding energy of organic compounds such as flesh". After being consumed, their victims are left like mere husks which easily fall apart.

Culture and society
The Nimons' modus operandi consists of moving from world to world, posing themselves as gods and devouring the entire population within a few years. They are able to create artificial black holes using a maze-like Power Complex.

When the time arrives for them to move to their next planet, the Nimons send a single agent through the black hole in a small vessel, to search for an appropriately primitive or decadent civilization. After arriving there, the Nimon poses himself as a god-like figure, claiming to be the last of his race and promising highly advanced technology to the natives in exchange for sacrificed victims to be consumed by him, and for material supplies that will enable him to build a second Complex and link it with the one on the previous world where the rest of the Nimons remain waiting. Once the connection is made the Nimons migrate en masse and consume the entire population of their new planet.

This cycle was broken by the Fourth Doctor, who prevented the Nimons from invading Skonnos and destroyed their black hole machine, leaving the Nimons trapped on the dying world of Crinoth, which soon exploded. It is likely that the Nimon species became extinct after this.

Appearances

 * Doctor Who Season 17 - The Horns of Nimon (1979)
 * Big Finish's Doctor Who audio stories - "Seasons of Fear" (2002)