Marshchild
From Tardis Wiki, the free Doctor Who reference
The Marshchild was a young Marshman who followed the Doctor into the Alzarian ship. It was soon captured and taken for experimentation by Dexeter. Just as it was about to be operated on a psychic link with Romana caused it to go berserk, killing Dexeter and eventually itself when it broke a panel and was electrocuted. (DW: Full Circle)