The Headmen was a group of villains that all suffered from traumatic head injuries, which were in most cases self-inflicted. The brilliant transplant surgeon Arthur Nagan had his head grafted onto the body of a gorilla by apes he previously experimented on. Seeking help with the development of a new serum, Nagan allied himself with the scientist Jerold Morgan who accidentally shrank his facial bones while conducting an experiment of his own. The two of them created a lab in Westbury, Connecticut, where they met the charlatan Harvey Schlemermen. Schlemermen was injected in the brain with a serum created by Nagan and Morgan; the serum gave him the ability to tap into an other-dimensional, rage-inducing "Black Rain." The last member of the group was Thursday Rubinstein; a scientist and doctor who replaced her head with organic circuitry, which was programmed to grant her head with offensive and defensive capabilities.
They became devoted to world conquest through manipulation of politics, business and social movements, and their bizarre schemes were repeatedly thwarted by the Defenders. They've also gone head-to-head with Spider-Man and She-Hulk. One the Headmen's plots included shrinking the White House, its occupants, the Defenders, rival would-be world conqueror Nebulon and his army of Bozos, trapping them in a glorified ant-farm through which the Headmen hoped to study human society indefinitely in miniature.