Etydion

Etydions are a sapient species regarded as the most powerful telepaths in the universe, with the power to read and influence minds as they please.

Biology
Etydions are green-skinned humanoids with elongated paddle-like arms or flippers. Their DNA seems to have viral properties that allow it to infect other creatures and slowly transform them into Etydions. However, this process can be reversed by an Etydion's telepathic influence.

History
In the past, Etydions were highly sought after for their telepathy. They would offer their services to invaders and conquerors, who used an Etydion agent to implant fear into the minds of enemies and make them defenseless. At some point, however, the survivors of several conquered planets joined forces and destroyed the Etydion homeworld, eradicating the species.

Appearances

 * K-9, s01e19, "The Custodians" (2010)