Gog is a character inspired in the graphic novel Kingdom Come. As both authors of that novel, Mark Waid and Alex Ross went in different ways, there were two versions of the character: the first one, (by Waid and Jerry Ordway), known as William Matthews appeared in New Year's Evil: Gog #1, (February 1998). The second one was created by Alex Ross, Geoff Johns and Dale Eaglesham, and appeared in Justice Society of America #13 - Thy Kingdom Come: Supermen (February 2008). Both characters are supposedly be tied to the character from Kingdom Come Magog.
Eventually both characters were tied together by retcon.
Gog, the god from the Third World, was a giant towering figure with elements resembling both, Highfather (clothes) and Darkseid (skin and facial features). He used a golden helmet with horns and had red eyes.
Thy Kingdom Come
Gog was from a paradise known as the Third World, his world was destroyed when the old gods waged war across the land. Gog refused to choose a side and was cast out. He then plunged himself into the bleed traveling from world to world. He claimed, that he is not responsible for the actions of the fake Gog (William Matthews), who after Gog emerged, made him loose the identity due to the fact that Matthews is going mad of visions from different realities.
As proof of his good intentions, Gog preformed a number of miracles both to places and people, as well as members of the JSA. His first task is to set up an encampment, and while doing so, is joined by followers. He then heals a village from the toxic wastes that were being emitted from lava that protruded from the mountain that he was embedded in. The JSA member Damage then approaches Gog because he, like most other JSA members, are skeptical of Gog's intentions. Gog responds by healing the scars and disfigurements on damage's face, who after this becomes one of Gog's greatest believers. Continuing his miracles upon JSA members, Gog heals Starman's schizophrenia, gives Doctor Mid-Nite his sight back, and sends Power girl back to her home reality of Earth-2. Gog then finds a small battle occurring at a near-by village and goes to stop it. When arriving, Gog finds the villagers being attacked by a group of ruthless soldiers, Gog acts by turning the soldiers into trees. During the battle, the JSA member Lance is blasted by a rocket launcher, and dies. Gog revives Lance though, and replaces his destroyed arm with gold armor, and renames him Magog. After the battle, Gog gains more followers by the likes of the villagers he saved, and JSA members Hawkman, Judomaster, Amazing Man, Tom Bronson, Damage, Magog, and Citizen Steel, much to the rest of the JSA's dismay. Gog then tells his followers of his plans to reach the middle east, and destroy the corrupt militia forces there as well. On the 6th day of his activities, Gog asks for a day of rest, in which he sends some of his followers to preach his "word".
On the 7th day of his time on earth, Gog tells his followers to get down on there knees and worship him for the miracles he has bestowed. While being taken aback by this, it is shown that Sandman has discovered Gog's true intentions: rooting himself to the earth with the consequence that when he leaves, the earth will die. The JSA arrive at his encampment with plans to remove his head from his body, the only way Gog can die without the world dieing as well. As his followers attempt to protect him, they quickly change there mind when they see him try to transform Jay Garrick into an actual lightning bolt. Gog retaliates by taking away all of the miracles he bestowed, leaving all of the JSA members as they were before he had come.
The JSA finally prevail, and sever Gog's head from his body. Kingdom Come Superman and Starman then finish things by taking Gog's head to the Source Wall, and embedding it there forever.