Forty (Morphology)

 was a Kobold from Procyon Two. He and two others, Forty-Two and Two, came to Earth in search of the Third Doctor and Jo Grant.

The Kobolds kidnapped Jo in order to get into the TARDIS. Once inside, however, Forty and Two were accidentally killed by a Doctor-created device that Sergeant Osgood brought into the TARDIS. (PROSE: Morphology)