Marshchild

The Marshchild was a young Marshman who followed the Fourth Doctor into the Alzarian starliner.

Biography
The Marshchild was soon captured and taken for experimentation by chief scientist Dexeter. Just as it was about to be operated on, a psychic link with Romana II made it go berserk.

The Marshchild attacked and strangled Dexeter to death, before being attracted to an image of the Doctor — the only person who had shown it any kindness — on a video screen in the laboratory. To the Doctor's horror, the Marshchild punched through the screen to try to reach him and was electrocuted. (TV: Full Circle)