The Chimeras were genetically engineered supersoldiers created by Torchwood 1.
Profile
They were created by splicing alien DNA with that of an ordinary Human creating a hybrid soldier for the British Special Forces for use in the War Against Terror. The creation of the creature was under the supervision of Rupert Howarth. The resulting creature was uncontrollable and unpredictable resulting the project being shut down but not before the Chimera escaped. It was determined in tracking down its creator and kill him.
The Chimera was capable of smelling the fear in its target and used this ability to track down the victim. A further extension of this ability was the capacity of appearing as its victims worst fear. The lone Chimera managed to locate its creator and kill him but it too was also killed through the injection of a cocktail of drugs that were hidden in [[Torchwood 3]. (TWC: Legacy of Torchwood One!)