Krogg

Krogg

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 he 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 Superman 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, Dec 1977: "Save My Friend, Kill Your World!"—SF No. 187, Feb 1978: "A Phoenix of Steel!").