Satan, un lutteur qui a vendu son âme au Prince des Ténèbres en échange de la gloire, mais qui a été contrecarré par l'ancêtre de Santo, ressuscite cent ans plus tard avec une armée de momies et est bien décidé à se venger.
In the swamps of Savannah Georgia, Dr. Alec Holland works with his sister Linda on a top-secret bio-engineering project to create a plant/animal hybrid capable of thriving in extreme environments. Government agent Alice Cable arrives just as Holland makes a major breakthrough, and begins to develop feelings for him. However, a paramilitary group led by the evil Dr. Anton Arcane, who is obsessed with immortality, kills Linda while trying to steal the formula for their own purposes. During the attack, Alice escapes and Alec is covered in chemicals, caught on fire, and runs screaming in the swamp, presumably to die. However, he returns as a monstrously mutated plant creature. As the Swamp Thing, Holland battles Arcane's forces to protect Cable, and eventually takes on Arcane himself, also mutated by the Holland formula.
While everybody else is preparing for Adam's and Adora's birthday, Adam is helping Man-At-Arms finish up the Sky Spy, a space shuttle intended to spy on Skeletor. The moment they head back to the palace, though, Orko gets inside the ship and messes around with the controls, causing the ship to blast off into the sky with him in it. Skeletor catches sight of the aircraft and, despite not knowing what it is or who is flying it, he gives chase after it in the Collector. Before he can take it down, He-Man and She-Ra, who are also unaware that Orko is in the Sky Spy, show up and punch a hole in the Collector, throwing it off course.