The Prometheon was a massively powerful giant creature that was released on earth and sought to absorb all the heat it could find.
The Prometheon was an artificial creature created by an unnamed alien race that intended to use it for heavy labor and its fuel was to be heat from the twin suns of the planet. However, they had granted the creature intelligence, which, however minimal was still enough to grant it the ability to make its own decisions. Seeking greater sustenance, the creature went on a rampage destroying everything around it hoping to create fire and thereby gather up more fuel. And as it gathered more heat, it gained in strength. The aliens managed to stop the creature and strapped it to an asteroid and sent it into space with a warning transmitter to prevent others from releasing it.
Some time later, the Prometheon's asteroid reached Earth and was on a collision course with Metropolis. General Hardcastle was assigned to destroy the asteroid to prevent it from killing the people of the city. Hardcastle's intentions remained the same when he saw that the Prometheon was strapped to the asteroid and after the creature awoke from its coma after being exposed to the sun he detonated the charges. The asteroid was destroyed and the Prometheon fell to Earth. It was unharmed by the massive heat generated by falling through Earth's atmosphere as it simply absorbed the heat from entry and gained in strength.
Landing in the ocean, it set about to search for a source of heat. It first grabbed hold of a nuclear submarine and absorbed the heat from the reactor. After Superman took the submarine, the creature continued its search and eventually made it to land. Once it reached the surface, Hardcastle's forces attacked the creature and it contentedly stood its ground absorbing the heat from the explosions. However, after being hit by NX Gel missiles, the creature’s hunger spiked and it went to Metropolis to seek more sources of heat.
It first absorbed the heat from molten steel at the Steel Mill and was then confronted by Superman. While Superman was strong enough to hurt the creature, it seemed to take him as an annoyance and proceeded to swat at him like he was a fly. However, power to the city was cut off and the creature suddenly found itself in a cold wasteland. It desperately sought out another source of heat but was unsuccessful until Superman superheated an I-beam. It ravenously followed Superman into a lake but lost interest when it saw the moon. Equating the moon's light as a source of heat, it stood looking to absorb more fuel. However, Superman managed to ignite a boatload of gasoline and the creature went after it. When the Prometheon was fully in the lake, S.T.A.R. Labs dropped two kinds of chemicals that would create instant cold and the creature was frozen. Its current whereabouts are unknown.
Powers and abilities
The Prometheon was a considerably strong creature, having the strength to move mountains, hurt Superman, and hold a nuclear submarine running at full throttle. It was also said to gain in strength as it absorbed more heat. Cold seemed to reverse this effect.
It also held a degree of invulnerability that made it capable of surviving the impact of striking the ocean from a altitude greater than that of Earth's atmosphere, while bombardment by military ordnance caused it no discomfort. Only Superman seemed to be able to hurt the creature and though annoyed by his efforts, the Prometheon didn't seem to sustain any great damage.
Because it was designed to absorb heat as fuel, the creature was capable of absorbing heat from nearly any source (it never seemed to absorb body heat even when it had Superman in its clutches). This ability allowed it to cool a nuclear reactor, soak up the fire from incendiary weapons, and turn molten steel into solid steel. Any fire that touched the creature would also be absorbed directly into its body.
Though the Prometheon itself is not an established DC character, its name and prison resemble the Giants of the Promethean Galaxy, an invention by Jack Kirby as part of the Fourth World. The giants existed before the rise of the New Gods. In their hubris, they sought to breach the Source Wall. For their transgressions, they were imprisoned by the Source in the Promethean galaxy, chained to massive celestial bodies, which served as their own machines for breaching the Source. These stone giants bind themselves to large weaponized comets in an attempt to smash the Source Wall.