A monstrous, mace-wielding behemoth from an unnamed extra-dimensional realm similar to the Phantom Zone that exists between the dimensional barriers separating Earth-1 and Earth-2. Krogg is accidentally set loose upon Earth-1 by the Superman of Earth-2 when he attempts to travel to Earth-1 to enlist the help of Jimmy Olsen to save the life of his friend, Jimmy Olsen of Earth-2. At the exact moment that the Earth-2 Superman attempts to traverse the dimensions, Professor Potter is experimenting with the Justice League of America's Transmatter Machine aboard their satellite headquarters, and thus unleashes Krogg upon Earth-1.
Krogg separately battles the Superman of Earth-1 and his Earth-2 counterpart, defeating both easily. Using the Transmatter Machine, Professor Potter temporarily combines the two Supermen into one being to battle the interdimensional monster. This Super-Superman, as Professor Potter calls him, is able to apparently destroy Krogg by increasing his internal energy, causing him to reach critical mass and explode (SF No. 186/2, Nov/Dec 1977: "Save My Friend, Kill Your World!"; SF No. 187/2, Jan/Feb 1978: "A Phoenix of Steel!").