The Cubes are flying cube-like searchlights that are one of the creations of the Duke of Zill alongside the Cylinders. They are used to monitered and detect anything out of the ordinary from every dark cornor. The Duke uses them to hunt down enemies and to search for those who disobeyed his "laws" and opposed his rule.
Like the Cylinders, the Cubes recieve their power from the Master Cylinder, the source of their energy.
But when Felix the Cat throws the sacred Book of Oriana at the Master Cylinder back at the Kingdom of Oriana in order to save his friends and defeat the Duke of Zill, it resulted in the sudden and quick destruction of the Duke's mechanical army and their energy supply, ending his evil forever.