Hailing from beneath the earth’s crust, the Inhumanoids were three elemental creatures with very bad attitudes. The de facto leader was Metlar, a volcanic type who could throw fireballs and had the power to animate statues. Tendril, a plantlike monster, had amazing regenerative capabilities and powerful tendril arms. Rounding out the trio was D'Compose, a frightening creature with an exposed ribcage who could turn any organic being into a zombie with a single touch.

Long ago, the Inhumanoids were defeated in battle by three other elemental factions known as Mutores - the rocky Granites (led by Granok), the mighty Redwoods (led by Redlen) and the magnetic Magnakor, who could split into two forms, icy Crygen and fiery Pyre. Teaming up against their common enemy, the Mutores banished the Inhumanoids to underground prisons, where they remained for untold years. Then some stupid humans dug them up.

Fighting for the side of humanity against the evil Inhumanoids were a group of scientists known as Earth Corps. Led by geologist Herc Armstrong, Earth Corps investigated mysteries beneath the Earth’s surface, while wearing powerful armored suits designed by group member Dr. Derek Bright (Bright’s suit had rock-cutting claws, while Armstrong’s contained a titanium grappling hook). Joining Armstrong and Bright in their Earth Corps duties were archaeologist/vehicle designer Ed “Auger” Augutter (green armor with a big drill for a right arm) and chemist/spelunker Jonathan “The Liquidator” Slattery (yellow armor, sprayed various fluids). Sandra Shore, the group’s benefactor, also donned a suit on occasion.

After hearing the Inhumanoids’ background from the Redwoods themselves, Earth Corps teamed up with the Mutores to take on Metlar, Tendril, D'Compose and their evil human flunky, Blackthorne Shore (Sandra’s brother). The group also had to deal with the terrifying, zombie-like Nightcrawler, a former associate of Blackthorne’s who had been turned into an undead monster by D'Compose.

The Inhumanoids series began not as a 22-minute cartoon, but rather as a 6-minute short, airing as part of the "Super Sunday" half-hour block along with other Marvel Productions shows, Jem and the Holograms, Bigfoot and the Muscle Machines, and Robotix. Although Bigfoot yielded only nine episodes, the other shows ran to 15 episodes, telling a complete story across their numerous installments, which were then cut together to form "movies" which were released to video.

Inhumanoids and Jem managed to surpass their fellow "Super Sunday" shows by going on to be turned into full-length shows. Jem achieved the greatest success, eventually running to 65 episodes across several seasons, while Inhumanoids lasted only one season. In both cases, to begin the series, the "movies" were re-aired, cut into separate 22-minute episodes consisting of three shorts each, yielding a five-part miniseries. In the case of Inhumanoids, this miniseries was given the series subtitle, The Evil That Lies Within. A further eight 22-minute episodes were then produced, yielding the standard thirteen episode season.

Inhumanoids wasn’t a cartoon for the very young or very claustrophobic. It had its lighter moments, but many battles took place in spooky caverns and deep crevasses, where, in the words of the theme song, “nightmares begin.” But for those old enough to appreciate it, Inhumanoids was another action-packed wonder from Marvel/Claster, the team behind Transformers and G.I. Joe: A Real American Hero.