The Eriscents were a telepathic species.
Biology
Eriscents were under four feet tall, with pale skin and relatively featureless heads. They communicated via telepathy. However, non-Eriscent minds were usually unable to handle mental contact with Eriscents. This often resulted in epileptic seizures and death. (PROSE: The Straw that Broke the Camel's Back)
History
An Eriscent spaceship crashed on Earth in 1969. The Third Doctor was forced to kill it, because the attempts at telepathic communication it was making were unintentionally killing people. (PROSE: The Straw that Broke the Camel's Back)