Mechanical Beasts are the robotic troops originally used by the Mycenae Empire back when the large Mechanical Gods landed on Earth, they were uncovered and later used by Dr. Hell in his plot for world domination.
The Mechanical Beasts stand over 20 meters tall and are armed with a variety of weapons such as missiles, blades, and beams. They were originally controlled by the biomechanical Kedora which gave the Mechanical Beasts a vicious battle nature. Alternatively, they can be controlled by commands from certain individuals like Archduke Gorgon. After Dr. Hell uncovered them, he had a brainwashed Kenzo Kabuto reprogram the robots with an AI that had them function as if they were driven by instinct. Dr. Hell could control the Mechanical Beasts through a special rod that was regularly given to Baron Ashura.
The Mechanical Beasts originally came as foot soldiers for the Mechanical Gods as they came to Earth to set it up as a strategic point for an intergalactic war. However, Zeus broke ties with his old home after getting a liking to the native humans. Hades in a plan to take control of the Mycenae Empire, used Mechanical Beasts to try and overthrow Zeus but failed with his body destroyed. But Hades' soul sunk Bardos into the sea, never to be seen for thousands of years. Dr. Hell and a few colleagues later discovered the Mechanical Beasts sealed behind a statue of Zeus among other Mycenae artifacts. Taking control of Kenzo, Dr. Hell has him reconstruct the Mechanical Beasts for his plans of world domination.