Nedenah

The Nedenah, called "Greys" by Humans, were a species of explorers.

Biology
The Nedenah were humanoid, with pale skin, large green eyes and large heads. They were mildly telepathic and were capable of giving off a sense of calm. They had brown and yellow blood. (PDA: The Devil Goblins from Neptune)

Technology
The most well-known Nedenah technology were their flying saucers. They were large, featureless, pale-coloured disks. They were capable of moving 30 times the speed of sound, could stop in a second and were highly manoeuvrable. Though they were opaque without any windows, the Nedenah would navigate by the ship telepathically beaming the view from outside. The hull could also be shed if it was damaged, leaving an undamaged hull underneath. (PDA: The Devil Goblins from Neptune)

Other technology was also taken from the wreckage of a crashed Nedenah ship, much of it adapted by the American army. (PDA: The Devil Goblins from Neptune) The technology for broadband internet was also derived from the Roswell crash. (DW: Dalek)

History
The Nedenah had been visiting Earth for thousands of years. They were known to the Aboriginal Australians for much of this time, and were believed to be deeply connected to the Earth.

In 1947, a Nedenah ship crashed in Roswell, New Mexico. The 3 survivors and the remains were taken to a secret government base, though one was killed on the way. A year later, another ship was sent to find the survivors. The American Government was able to fight it off, taking one survivor, though they had major difficulties. By the third attempt, the technology had been reverse-engineered and the Nedenah were shot out of the sky before they could attempt anything. At this point, they stopped trying to save the captured Nedenah. Though most of the Nedenah were captured, some were secretly kept safe inside of the ships.

In 1970, the Waro were invading Earth when they learnt of the Nedenah prisoners. They forced their agent Viscount Rose to try to kill them, as well as attacking the base themselves. At the same time, Brigadier Lethbridge-Stewart had been captured and had been brought to the same base. He was able to free the Nedenah, who took back their ship and used it fight off the Waro. They then removed all of their technology that they could find and left Earth. (PDA: The Devil Goblins from Neptune)