Thrint

The Thrintun (or Thrint in the singular) are a race of aliens who have been extinct for at least 1.5 billion years. They are telepathic sentient creatures who once had control over the entire Milky Way, hence their alternate name of "Slavers".

Physiology
The Thrintun are humanoid carnivores with green skin and scales. They feed and excrete through a single orifice on their face which has sharp teeth and tendrils with which they feed. They have one large eye in the middle of the forehead, and they had large round heads. Each hand had three large fingers. Thrintun did not have a bodily function that regulated their appetites. In their early stages of development, one of the necessary tests for the young ones to undergo would be the control of one's feeding in order not to become sick from eating too much in an attempt to satisfy their insatiable hunger.

Telepathic Power
When they existed, the Thrintun had absolute power over the galaxy because of the telepathic ability they exhibited, called The Power, which was also a very effective form of mind control. Thus, the need to hunt was eliminated because they could merely call their prey to them and wait to be killed and consumed. As children, a male would be considered an adult when they were capable of resisting the telepathic mind control of the father.

However, it is revealed that the Thrintun are not a particularly intelligent species. Much of the technological advancement they made over the centuries of their galactic control was actually developed by the more intelligent races they had control over. Males typically had an IQ of below average when compared to the normal human, while the females had practically no intelligence to speak of, to the point that they were considered to be non-sentient.

Nevertheless, their lack of intelligence was well-supplicated by The Power, and as a result, natural selection never made it much of a necessity for the Thrintun to evolve any farther than they already had, whether physically or mentally. Their society was not very complex, and they had only basic philosophies to live by. It would be interesting to note that all their religions revolved around The Power and how it was part of their destiny to take over the entire galaxy.

Because of this, a Thrint born without this telepathic ability was considered to be unworthy to live by many of its species. It was set apart from the rest of the Thrintun and was called a Ptavv. If they were not killed by their family at birth, they were instead tattooed pink and became slaves to the Thrintun along with the rest of the other races in the galaxy.

Post-extinction
A race of aliens called the Grogs are said to be a species which devolved from the Thrintun, and share a telepathic mind control ability much like that of their supposed ancestors. However, they claim to have no knowledge of the Thrintun.