Nightmare(s) 1 and 2
The predecessors of Nightmare 3. Unlike 3, they aren't living weapons and are mechanical. They were deemed failed because the amount of power required to use this kind of machine would leave the Golden City powerless.
A monstrous creature found in an abandoned lab within the Golden City, it was created by several scientists and was nicknamed Nightmare 3 because of it's large, scary, bat-like appearance. The door to the lab was sealed, and the scientists - along with everyone else in the city - left because of the creature.