- You may be looking for Carmentine Mind Leach.
The Mind Leeches were a species encountered by Dr Elizabeth Klein, Colonel Lafayette and an incarnation of the Master posing as the Doctor in an office block in the city of London. They came from another dimension and fed on intelligence, causing a number of the building's occupants to act unusually. When UNIT stormed the building, the leeches attacked the soldiers, resulting in Private Oscar Phillips losing his mind. (AUDIO: UNIT: Dominion)