The Gravity Generator is a powerful device developed by the Astral Knights, on Bomberman 64: The Second Attack. It could expand the Dark Matter in a galaxy by a minor way, resulting in a massive devastation of it. They used the device to empower their own planets with the infinite dark energy power. In the game, Bomberman must destroy all the power cores in the gravity energy rooms related to this device, in order to get to other planet/level. In some instances, the power cores must be frozen before they can be destroyed.
There is a similar generator located in the Warship Noah that uses the same kind of technology but its actual power is unknown.