Long ago, the Necro Monster came to Earth on a meteor. Landing in North America, it drew the Natives to it, promising wealth. But the native humans proved too strong of character to listen and created a spear end out of the meteor on which it came. But before they could destroy it, the Necro Monster telepathically called out to Europe, summoning men who were driven by greed. One such man was C.F. Vopelhart, who killed the Native wielding the spear. Given incredible wealth, his financial empire expanded as the creature extended his life. He soon regretted letting it live, and tried to destroy it, but he was mentally fatigued over the years under its influence. He tried to warn others not to seek out the gold the creature offered but they didn't listen, ending up in pods that filled them with their worst fears until their bodies expired.
One of the creature's latest victims, Ryan, Angel's brother, drew the attention of the Turtles, who with the help of Volpehart, try to destroy the creature, but they end up trapped in pods. Leonardo is able to fight it and free his brothers. The creature tried to influence him directly, rising up from the depths, but he rejected the control and threw the spear in the creature's forehead, seemingly destroying it. At this, Volpehart crumbles to dust, earning peace from his centuries long life. But as the Turtles leave his tower, a nearby telephone rings, which a passing businessman picks up. Immediately, the creature's voice influences him, implying that the creature is not dead, and that it has a new servant.
Though alien in nature, the Necro Monster takes obvious cues from the monstrosities in H.P. Lovecraft's Cthulhu mythos. In particular, its appearance closely resembles that of Cthulhu himself. Its domain, with its inscription above the door ("Abandon all hope ye who enter here", cribbed from Dante's Divine Comedy), and nightmarish geography, echoes popular interpretations of Hell.