A Leech Command is a large black device that can drain power from other sources. Megabyte built a large Leech Command so that he could drain power straight from Game Cubes. He wanted to break into Mainframe's Archives to steal the command circuitry for the Gateway Command. To do this he built a large Energy Drill to penetrate the security barrier under the floor of the Archives, but it needed power to do this. The Archives have a security field second only to the Mainframe Core, so Megabyte would need as much energy as the Core to break the security field. The only source of that much energy, except for the Core, is a Game Cube.