Men in Black

The Alliance of Shades was an organization created to hide alien activities on primitive planets like Earth. They used android agents to remove any signs of alien activities, including any witnesses.

In 1958, four androids, including Mister Dread, were obtained by Lord Azlok and were sent to find Rivesh Mantilax and his weapon. They were damaged by Night Eagle and his tribe, though Mister Dread was later repaired.

In 1972, the alliance discontinued their robotic agents. (DW: Dreamland)

Behind the Scenes
According to the Tenth Doctor, the other members are called Mister Terror, Mister Fear and Mister Apprehension, but it is unknown if it was just a joke on Mister Dread's name.

The Alliance of Shades was inspired by the popular UFO conspiracy theory of the Men in Black (MIB), these being government agents dressed in black suits who reportedly harass or threaten UFO witnesses in order to keep them quiet about what they have seen.