Superman is a hero on the planet Earth who has occasionally been drawn into the affairs of Eternia, where he has sided with He-Man against the evil forces of Skeletor. He is known by reputation on Eternia, by way of the stories told by the Earth woman Queen Marlena.
The last son of the planet Krypton, Superman was born Kal-El shortly before his homeworld's destruction, and sent to Earth in a spacecraft by his parents. Raised by Earth people as Clark Kent, he developed superhuman abilities in his new environment, and decided to use his powers in the fight for good. Although he lives his normal life posing as a mild-mannered human journalist, he employs his Superman alter ego whenever he must defend his adopted homeworld against the forces of evil.
Superman possesses many super powers, due to the differences in solar radiation and gravitational pull between Earth and Krypton. Among the heroes of Earth, he is considered one of the most powerful. Although Superman may well be stronger than He-Man, he has no defense against supernatural forces--a vulnerability that is particularly dangerous in Eternia.
In advance of its Masters of the Universe limited series, DC Comics began promoting the Masters of the Universe characters with two stories featuring its headline character Superman encountering the world of Eternia. DC Comics Presents, a series dedicated to stories of Superman teaming up with various guest-stars, introduced the Masters of the Universe characters into the DC Universe with issue #47, "From Eternia -- With Death!" He-Man knows of Superman, but he cannot explain that he learned about the Kryptonian from stories told by his Earth-born mother, since this might expose his secret identity as Prince Adam.
Following this adventure, a free preview story called "Fate is the Killer" saw Skeletor actively scheming against Superman to prevent his interference during an attempted raid on Castle Grayskull, although in the end the Man of Steel and Eternia's champion still thwart his plans.
Masters of the Universe Classics
Due to Mattel holding the rights to produce toys based on the DC superheroes, it became possible for the company to release a series of "crossover" two-packs with Masters of the Universe Classics figures squaring off with characters from the DC Universe. The first of these was naturally a He-Man vs. Superman set, packaged with a reprint of "From Eternia -- With Death!"