The Talichre were a race of alien invaders who came to Earth in the late 20th century. They were described as large and "blobby". They also invaded Anima Persis at some point, as well as several other planets.
When they first invaded, UNIT sent in five men, including the Third Doctor, Andy and Michael. During this invasion, the Doctor stole one of the Talichre's devices. In order to get him to return it, one of the humans working for them killed Andy, which greatly disturbed Michael. (PDA: Relative Dementias)