Masters of the Universe
In July 1982, (DCCP No. 47, "From Eternia--with Death!"), Superman was patrolling the skies of Metropolis when he saw a "distinctly unearthly" cloud, a cloud which he was unable to penetrate with his X-ray vision. As he approached it, he began to feel very weak, and was drawn into it by a mystical force.
He soon found that the cloud was a gateway to the planet Eternia, and was a byproduct of an attack by the evil demonic Skeletor on Eternia's Castle Grayskull. (Castle Grayskull was a protectorate of the Masters of the Universe: He-Man, Teela, Man-at-Arms, a talking Tiger, and a Sorceress of divine origin.)
Superman, Skeletor, and his henchman Beastman engaged in battle. Skeletor was impressed by Superman's amazing strength; nevertheless, the Man of Steel was no match for the mystical forces under the command of Skeletor, who threw Superman into the base of a nearby hill.
He-Man arrived on the scene and immediately recognized Superman, since his own mother was a traveling Earth-woman. No sooner were the two properly introduced than Skeletor cast an enchantment that effectively controlled Superman's body and locked the two titans into battle. Superman was soon victorious over He-Man, and Skeletor commanded him to smash down the doors of Castle Grayskull...but before he could complete the terrible task, Superman was able to distract Skeletor with his heat vision and break free of his spell. He subdued Skeletor before he could cast another enchantment.
In November of the same year, Superman once again encountered the Masters of the Universe (DCCP No. 51: "Fate Is the Killer"). While the space-traveler Zodac challenged He-Man after traveling through the Multiverse, Superman was sucked into an underwater vortex and deposited in Eternia. Superman's entry into Eternia was once again due to the meddling of Skeletor, who sought the other half of a power sword that lay on the bottom of one of Earth's oceans. Superman quickly grabbed the power sword and hurled it before Skeletor could reach full power.
Zodac was intentionally trying to lure He-Man away from a fight with Skeletor, in order to save his life. However, He-Man proved victorious and came to Superman's aid. A battle ensued, and He-Man and Skeletor struck one another down, He-Man with Skeletor's own power sword, and Skeletor with a magical blast. Zodac arrived too late, assuming that He-Man was dead...however, he was merely knocked unconscious by the blast.
At the battle's end, a dazed Superman stood up, wondering exactly why he was on Eternia in the first place.
