A psychic species was used for security at the Bank of Karabraxos. One called the Teller was used to read the customers mind to search for criminal content. If any was found it turned his/her brain to "soup", according to the Twelfth Doctor. The other known member of this species was a female locked up inside a vault that was opened by the Doctor. He dropped them off on a planet with grass where they lived together.
They both were large and had an eyestalk on either side of their head. (TV: Time Heist)
After the Twelfth Doctor's mind was connected to a mind scythe, the "holiday snaps" the Doctor showed Kygon Brox included the Teller. (COMIC: The Instruments of War)