Mendel Stromm was sickly growing up, but discovered a love of gadgetry and robots that helped him get through an unhappy childhood. As an adult, he became Norman Osborn's business and scientific partner in the early days of Osborn Industries until he was caught embezzling and Norman had him arrested. On his release from prison ten years later, Stromm wanted revenge on Osborn and sent robots to destroy his livelihood. Spider-Man stopped the robots and captured Stromm, saving him from being shot by Osborn, only to see him apparently die from a heart attack. Stromm's robots reappeared soon after which led to the discovery of the Robot-Master, a robot duplicate of Stromm, who had transferred his memories to it shortly before his "death". It was quickly disposed of by Spider-Man.

Years later, Norman Osborn became curious about the unexpected effects of the Green Goblin formula of which Stromm had developed the prototype. He had Stromm exhumed and discovered him alive, due to the formula, although his body was a withered husk. Revived, Stromm, now Gaunt, was given a promise of rejuvenation if he carried out Osborn's plans to ruin Peter Parker. Given the use of Multivex's extensive resources by Osborn, Stromm blackmailed Seward Trainer into developing the regenerator, and hired the Hobgoblin, Arcade, and Cell-12 in a succession of attempts to either harm or kill Ben Reilly and others.

Successfully rejuvenated, Stromm, clad in robot armor and calling himself the Robot-Master, attempted to kill Reilly himself, but failed. As a consequence of his failure, Osborn zapped him with a concussive blast and left him for dead. He came to with severe burns to his head and loss of memory. While wandering aimlessly, he stumbled across his original hideout and began making toy robots for hospitalized children. Unfortunately, mention of Osborn's name brought back Stromm's thirst for revenge, and he became unhinged before Spider-Man stopped him. At Ravencroft, Dr. Kafka discovered that he had no memory of the previous nine years. Stromm was treated and released. Obsessed with terminating Spider-Man, he attempted a new technique, interfacing his brainwaves with a computer that would enable him to control robots by mind power alone. The computer started to take over Stromm's mind, decapitating him, and seizing control of New York's computer infrastructure. Stromm used the small amount of control he still had to lead Spider-Man to his base underground, asking him to kill him before it was too late. With the help of Peter Parker's hacker friend Shea Tinker, Spider-Man introduced a recursive virus into the Machine, which sent Stromm and the Machine into standby, until Spider-Man could figure out a way to help Stromm permanently without killing him.

Recently someone gave anonymous tip to F.B.I. where they could find Stromm. S.H.I.E.L.D. operatives found him connected to the computer and managed to remove him from the Machine. He then was given choice either register and work for them or go to jail. He happily registered and was given new robot body. He was ready to live quiet life with his new robots but he soon was visited by Penance (Robert Baldwin), who was on a quest to revenge the innocent people and his team mates in New Warriors who Nitro killed when he destroyed part of Stamford, Connecticut. He made Stromm tell the launch codes to American nuclear missiles so he could use them against Latveria where Nitro was held prisoner. In reality he just wanted the codes to lure Thunderbolts to the silo and steal their transport. Stromm was found locked into a sarcophagus that he had in his vault by S.H.I.E.L.D. agents.