He is the reason why many of Iron Man's supervillain enemies have access to extremely advanced technology and why these foes use their equipment for violent crimes instead of profiting by bringing the designs to market.

These villains are his underworld mercenaries, secretly armed and contractually obliged to fulfill missions against Hammer's competitors and enemies, such as Tony Stark.

[2][3] Layton himself recalled in a 2014 interview that he and Michelinie originally created Hammer as the cautionary tale of what kind of person Tony Stark might have become if he stayed on his path as a global war profiteer, as well as a tribute to actor Peter Cushing; in Layton's words, Stark and Hammer are essentially in the same line of work, but with diametrically opposed moral views.

[5] In exchange for fifty percent of the crime profits, he would pay bail for costumed criminals and finance the development and replacement of both their weaponry and equipment.

In the event that a mercenary under his employ violated his contract, Hammer would send an enforcement unit, usually led by his most reliable supervillain employee Blacklash, to attack the rogue and confiscate his assigned equipment.

At the start of the Demon in a Bottle storyline, Hammer invented a device called the Hypersonic Scan Transmitter which allowed him to take control of Iron Man's armor.

Ultimately, Stark not only cleared his name and destroyed the control device, but finally learned that a major enemy was behind multiple attacks on his interests for years.

[20] With the Life Foundation, Roxxon Oil, Stane International and the Brand Corporation, he abducted a number of superhuman beings to analyze their abilities.

With operatives of HYDRA, Roxxon Oil, Moroboshi International and the Trinational Commission, he tricked the Masters of Silence into attacking Stark Enterprises.

[25] In the Earth X reality where Terrigen Mist mutates most of the world population, Hammer is murdered by Norman Osborn on his rise to being President of the United States.