The Vaalians, also known as the People of Vaal or Feeders of Vaal, were a primitive humanoid species native to the planet Gamma Trianguli VI. Their skin was reddish in color and they used face-paint. Their hair was gray-white and bushy. They were ruled by a self-aware machine named Vaal for 10,000 years. Every person on the planet were slaves to Vaal and revered it as a god.
The Vaalians were a peaceful people when the USS Enterprise made first contact in 2267. Shortly after the Enterprise landing party landed, Vaal deemed them as a threat and used the planet to kill several crew members, before instructing the Vaalians to attack the remaining crew members, killing one additional person.
In response to Vaal's attacks, Captain James T. Kirk broke the Prime Directive and ordered the destruction of Vaal, freeing the civilization from slavery. Until this destruction of Vaal, this group of individuals represented a classic example of a stagnant society, however, Kirk was optimistic about their chances for further societal development. (TOS: "The Apple")