The Steam Planet was a planet spared by the Anti-Monitor in an alternate universe.
However, it already consumed the planet's star's nuclear fuel. This was kept secret. Duke Nigel Fortenberry took control of the planet and forced it on an industrial sprint in order to generate enough power for a ray to open a rift to another dimension for the Anti-Monitor to consume. Duke Nigel continued to rule the planet with an iron fist and his factories became a symbol of his tyranny. Just as the planet lay on the verge of losing its star and freezing over, it was transported by Hal Jordan, Duke Nigel, and Steam Lantern to Jordan's home universe.