Thursday Rubinstein was a scientist and doctor who replaced her head with organic circuitry, she was shunned by a disgusted society. Equipping her head with offensive and defensive capabilities, Thursday turned to a life of crime, with the ultimate goal of replacing everyone's head with her circuitry. As Ruby Thursday, she joined a criminal group called the Headmen alongside Gorilla-Man (Arthur Nagan), Shrunken Bones (Jerold Morgan), and Chondu the Mystic. The quartet sought to rule the world and soon clashed with the Defenders. In their first encounter, Ruby almost single-handedly defeated the heroes. Ruby also downloaded Chondu's mind into an organic computer resembling his head and grafted it atop a monstrous form that revolted Chondu.
The Headmen put several complex plots into action, quietly infiltrating all levels of society. Posing as a normal human, Ruby started a political campaign in California under the slogan "new heads for old," but Defenders ally Jack Norris exposed her. The Defenders spoiled many of the Headmen's plots, including their plan to shrink many humans into a miniature society they could study and the Headmen were eventually defeated and arrested. Ruby later established herself in Las Vegas and partnered with the demon-like Dibbuk. Taking an interest in the fledgling hero Omega (the Unknown), she watched him closely, ultimately robbing him and causing his death when police mistakenly shot him while he pursued Ruby. Realizing Omega was composed of organic cybernetics, Ruby tried to steal his body from the morgue. The corpse suddenly changed places with James-Michael Starling, but before Ruby could determine what happened she and Dibbuk became embroiled in a complex battle between heroines Moondragon, Hellcat, Valkyrie (Brunnhilde) and Wasp and mysterious alien invaders. Ruby's head was ruptured during the fight, but she soon regenerated another, having kept a backup of her persona electronically.
Ruby rejoined the Headmen and they hired the Circus of Crime and Mysterio (Quentin Beck) to capture She-Hulk, cloning her body as a new host for Chondu's head, but She-Hulk and Spider-Man defeated them. The Headmen then sought Spider-Man's body for Chondu, but Spider-Man and the Human Torch (Johnny Storm) thwarted them. Ruby was briefly imprisoned alongside other cybernetic beings by the altered Doombot Mechadoom, then freed by the cyborg hero Deathlok (Michael Collins). The Headmen acquired control of the reality-shaping alien monster Orrgo, who granted them mastery of the entire world. Ruby used this new power to pursue her scientific interests until the Defenders reversed Orrgo's control. While in Paris, Ruby became romantically involved with criminal data broker Answer (Aaron Nicholson), but broke his heart when she left him unexpectedly. Later, she sought information from him, which she used to steal large sums of cash from A.I.M.; however, A.I.M. discovered her and hired Bullseye to assassinate her, Bullseye decapitated Ruby and killed her body, but the Answer secretly ensured her survival by keeping her head as a memento.
Regaining mobility, perhaps by attaching her head to a clone body, Ruby evaded capture by Hellcat after the Civil War|Superhuman Registration Act was passed, only to be apprehended by the Two-Gun Kid. Ruby and the Headmen soon appropriated a Doombot and programmed it to serve them. When the Heroes for Hire fought the Headmen, the Doombot killed Atlantean mercenary Orka, but Kung Fu master Shang-Chi savagely subdued the criminals, dislodging Ruby's head with a kick.
Ruby was eventually apprehended and detained in the super-prison called the Raft, where Wolverine, and the teleporter known as Cloak busted her out to help them defeat the mysterious Romulus. After Ruby was freed from her cell, the Raft guards locked the prison down and called in reinforcements in the form of Ares, the God of War, now working for the villainous Norman Osborn. Although, he was gravely injured Cloak was able to teleport Ruby to a nearby shore, while Wolverine and Skaar battled Ares. The savage pair narrowly escaped and were able to rendezvous with Cloak only to learn that Ruby had been taken by Romulus. The mysterious monster was able to persuade Ruby to turn against Wolverine and the others by threatening the life of her daughter, seeing that Ruby was not going to cooperate with their plan, Cloak teleported her back into the Raft prison.