The Bestiarus, also known as the Beast Men, were life forms genetically engineered as soldiers on an alternate Earth where Rome never fell.
They proved to be uncontrollable and smashed things without regard. They were deactivated and held in storage. Rome began using robot soldiers instead.
Centuries later, the Fourth Doctor used a control console to reactivate the Bestiarus, instructing them to start a revolution. They besieged the Malevilus spaceship, destroying the Malevilus that ruled Rome. (COMIC: Doctor Who and the Iron Legion)