Some TMNT stuff really isn't for little kids.
Null is an enemy of the Teenage Mutant Ninja Turtles and Mutanimals. He was perhaps the Turtles deadliest enemy surpassed only by The Shredder. Null claims to be the devil himself. Null appears in Teenage Mutant Ninja Turtles Adventures by Archie Comics.
A businessman wearing a purple leisure suit who was ultimately responsible for the death of the Mighty Mutanimals, when he contracted a group of cyborgs to kill them. The death was highly controversial and somewhat gory as a spread of machine-gun bullets tore the group down. He was also responsible for a three-part story arc in the Teenage Mutant Ninja Turtles storyline including the Four Horsemen of the Apocalypse; Death, Famine, War, and Pestilence. Null himself seemed to be somehow the leader of the group, giving orders to Death who in turn controlled the other horsemen like puppets. Null seemed to be somehow linked to hell. Originally the character had two small horns projecting from his forehead, and with every new deed of evil he committed he grew more demonic in appearance. Eventually he grew larger horns, a demon-like tail, and wings like a bat.
Null was a business man who initially appeared to be little more than a minor enemy to the TMNT, he was involved in projects that were destructive to the environment, heading up projects that involved slash and burn destruction of the South American Rain Forest, and dumping Toxic Waste into the Ocean. It was soon revealed that Null had sold the Earth to the alien Warlord Maligna, making the deal through her generals Scul & Bean, and was trying to exterminate mankind. To this end he struck a deal with a group of demons known as the Four Horsemen. But Null's plans were thwarted by the combined efforts of the Teenage Mutant Ninja Turtles and Mutanimals however. Null later created a team of cyborgs known as the Gang of Four, this team murdered the Mutanimals, but were destroyed by the Ninja Turtles. Null escaped into space at the end of the "Terracide" storyline, avoiding death unlike Maligna, and Slash. His current whereabouts are unknown.