The Creatures first came online through the Majin Heart Mother created by the Mycenae Empire after their successful invasion of Earth some time in the future. The emperor took control of the Grendizer when it came to Earth to help the resistance on Earth. However, desiring complete control in all eras the Emperor decided to allow Earthlings to create a method for time travel that not even Mycenae science and technology could create. To do this, he had the Creatures roam the Earth, ruling it for thousands of years while the resistance tried to find ways to fight back.
The Creatures hold complete control of the Earth while attacking any humans on sight. They believe themselves to be the superior species of Earth and that humans are just vermin. The Creatures are lead by the figurehead Great Leader Shamrock while Gallahan holds all of the true power in the Empire. The Creatures employ all sorts of tactics including kamikaze, never fearing death as many of the Creatures are able to be brought back through the Majin Heart Mother.