Death is the personification of the end of one's life, and is one of the Four Horsemen of the apocalypse.
Death was in league with the businessman Null who sought to avenge himself on the Teenage Mutant Ninja Turles and their allies the Mighty Mutanimals who stopped him from selling Earth to the alien insect Queen Maligna, the ruler of the Malignoids in return for the means of taking his business to other worlds.
Death seemed to be in charge of the Four Horsemen, controlling the other three members, War, Famine, and Pestilence through marionettes from his toy chest.
He also had the means to magically conjure up skeleton resembling creatures such as flying skulls, and a giant flaming skeleton with which he wanted to delay the Mutanimals from reaching his lair with by burning down large sections of a South American rain forest.
A formidable fighter, Death used his scythe as a weapon in melee combat. The scythe has magical powers that allowed Death to cut sections of reality into independent pieces. Though Death can temporary be defeated by making its skeletal body come apart, Death will eventually regenerate and re-assemble itself again.