Mendel Stromm is a former business partner of Norman Osborn. Osborn had him arrested under charges of embezzlement so he could assume full control of the company. It was Stromm's notes that provided Norman Osborn with the strength enhancing Goblin Formula that also robbed him of his sanity.
Years later, after he served his time in jail, Stromm attempted to revenge himself upon Osborn using a series of robots. He failed thanks to Spider-Man's intervention, and suffered what appeared to be a fatal heart attack when a then unknown would be assailant (later revealed to be Osborn on a Goblin Glider) fired a rifle through an open window.
Mendel Stromm was created by Stan Lee and Steve Ditko in 1966 and first appeared in The Amazing Spider-Man # 37.
During the years he was thought dead, a robot bearing Stromm's uncany resemblance caused problems for Spider-Man.
It was later revealed that Stromm had lived thanks to the same Goblin Formula he himself had created and administered, and had been in a state of suspended animation until Norman Osborn exhumed him and brought him back. He then became the cyborg robot master known as Gaunt thanks to Osborn's machinations and later killed Seward Trainer under Osborn's orders.
He attempted to kill Spider-Man (Ben Reilly) and Peter Parker with a trap he set consisting of seemingly normal human children, later revealed to in fact be more of his robots. It was then thought that Osborn killed Stromm again with a bullet to the head, but again, he survived and later went on to menace Spider-Man as a disembodied head.