A Morg
The Morgs are large sapient humanoids native to the surface of the planet Sigma Draconis VI. The population of Morgs on the planet were primitive, but plentiful. Because they possessed no organized civilization, they remained widely scattered throughout the planets surface.
At the peak of civilization on Sigma Draconis VI, it's inhabitants lived in a culture, advanced beyond 23rd century Federation capabilities. Around 8000 BCE, when a Glacial Age reoccurred, an underground complex was developed for the women, while the men remained above, causing a male-female schism. These men would de-evolve in the primitive beings known as the Morg.
When encountered by the crew of the USS Enterprise in 2268, they did not know the meaning of the word "female" or "mate" and feared "the others", whom they called the "givers of pain and delight". These "others" where later determined to be their female counterparts, the Eymorgs.
Below the surface of Sigma Draconis VI, the Morgs served as obedient "slaves" of the Eymorgs, by means of pain bands.
Following the disconnection of the Controller by the crew of the Enterprise, the Morgs and Eymorgs were forced to live together once again in an attempt to re-establish a civilization. (TOS: "Spock's Brain")
- The unnamed Morg credited as "Creature" was played by actor James Daris; on IMDB.