Dr. Jonas Harrow made his debut in The Amazing Spider-Man #114, published in November 1972. He was created by the prolific creative team of writer Gerry Conway and artist John Romita Sr.. Harrow's introduction occurred during the Bronze Age of Comic Books, a period characterized by more complex, morally ambiguous characters and grittier, street-level stories. Harrow perfectly embodies the era's archetypal “mad scientist” villain, but with a grounded, criminal twist. Unlike cosmic threats, Harrow was a man whose genius was corrupted by ego and a lust for power, operating in the shadows of New York's organized crime. His creation was part of Conway's effort to expand Spider-Man's rogues' gallery with threats that were not just physical but intellectual, forcing the hero to confront masterminds who manipulated events from behind the scenes. Harrow's first act—the creation of the visually distinct and formidable Hammerhead—immediately established him as a significant background player in the Marvel Universe's criminal ecosystem.
Jonas Harrow was once a highly respected and promising surgeon. His brilliance, however, was matched by an immense ego and a dangerous lack of ethical boundaries. He began conducting unauthorized and radical experiments, pushing the limits of medical science in ways his peers deemed monstrous. His obsession with unorthodox surgical techniques, particularly in the nascent field of cybernetics and neural interfacing, led to his being discovered. The medical community was appalled by his disregard for established protocols and human life. As a result, he was stripped of his medical license, publicly disgraced, and cast out, an event that left him deeply bitter and resentful. Instead of abandoning his work, Harrow embraced his new status as an outcast. He took his genius underground, offering his services to the criminal element for the right price. He saw the underworld not only as a source of funding but as a place where his “visionary” work would be appreciated without the constraints of morality. His ultimate goal was to prove the brilliance of his methods and achieve the power and respect he felt he was denied by the legitimate world. His first major opportunity came when he discovered a bullet-riddled, dying mobster in a back alley. The man was an amnesiac, his face and skull horrifically damaged. Seeing a perfect blank canvas, Harrow took the man to his secret laboratory. Through a marathon surgical session, Harrow rebuilt the man's entire cranial structure, replacing his crushed skull with a specially forged, flat-topped cranium made of secondary adamantium. When the man awoke with no memory of his past, Harrow provided him with a new identity: “Hammerhead.” He implanted in Hammerhead's mind an obsession with the gangster eras of the 1920s and a singular goal: to become the new kingpin of crime. Harrow intended to use Hammerhead as his pawn to unite and control all of New York's gangs, with himself as the true mastermind. This plan brought him into his first direct conflict with spider-man, who, along with doctor_octopus, thwarted the scheme. Though his puppet was defeated, Harrow's reputation in the underworld was made.
Dr. Jonas Harrow does not exist within the continuity of the Marvel Cinematic Universe (Earth-199999). His character, specific history, and creations like Hammerhead have not been introduced or alluded to in any film or Disney+ series to date. However, the thematic and narrative role that Harrow plays in the comics—that of a black-market scientist who provides advanced technology and biological enhancements to criminals—is a well-established trope within the MCU. Several other characters fulfill this function:
An MCU adaptation of Jonas Harrow could easily fit into the street-level narrative of properties like Daredevil: Born Again or a future Spider-Man film. He could be portrayed as a disgraced surgeon running a clandestine “chop shop” for criminals, offering cybernetic limbs, enhanced senses, or neural implants to those who can afford his services. This would provide a grounded, sinister threat and a logical way to introduce more technologically-based villains from the comics.
Jonas Harrow's threat comes not from physical power, but from his amoral, genius-level intellect and the technological wonders it produces.
Harrow is defined by the technology he creates for himself and others.
Harrow is arrogant, meticulous, and utterly amoral. He views other human beings, particularly his “patients,” as little more than clay to be molded or tools to be used. He is driven by a profound need for validation, seeking to prove the genius that the established medical world rejected. He is cowardly in a physical confrontation, relying on his creations, technology, or manipulated pawns to fight for him. Despite his brilliance, his ego is often his downfall, as he underestimates his opponents, particularly Spider-Man's resourcefulness.
As Jonas Harrow is not present in the MCU, he possesses no abilities or equipment within that continuity. However, we can perform a comparative analysis of the types of technology he represents versus what is seen in the MCU. Harrow's specialty is invasive, surgical cybernetics—the literal fusion of man and machine. This type of technology is less common in the MCU's street-level stories but has prominent examples elsewhere:
The key difference is one of scale and origin. In the MCU, such advanced cybernetics are typically the product of massive, well-funded organizations like HYDRA, a nation-state's black ops program, or a multi-billion-dollar corporation. Harrow, in the comics, represents a more “boutique” or “artisan” version of this—a single rogue genius operating out of a hidden lab. An MCU Harrow would likely be a former Stark Industries, Pym Technologies, or even Damage Control scientist who went rogue, taking his expertise to the criminal black market.
Harrow rarely has true allies, only clients, pawns, and creations.
In his debut storyline, Harrow positions himself to become the new crime lord of New York. He orchestrates a gang war between the forces of doctor_octopus and the remnants of the Maggia. The centerpiece of his plan is his new creation, Hammerhead, whom he unleashes to violently seize control. Harrow's plan is brilliant in its complexity, as he plays both sides against the middle. The plot brings Spider-Man into conflict with both Doctor Octopus and Hammerhead. Ultimately, Spider-Man discovers Harrow is the true mastermind. The story culminates in a chaotic showdown at Harrow's secret laboratory at a power plant in Westchester, which is destroyed in the ensuing battle. Though Hammerhead is defeated, Harrow successfully escapes, his reputation now cemented.
Years later, Harrow re-emerged with a more ambitious plan. Partnering with the Foreigner, he sought to create a new criminal syndicate to rival the Kingpin's. They recruited a diverse team of super-criminals, dubbing them the New Enforcers. Their plan involved systematically eliminating rival gangs and acquiring advanced technology. The storyline coincided with the “Maximum Carnage” event, and the New Enforcers tried to take advantage of the city-wide chaos. Spider-Man, along with venom and other heroes, confronted the team. Harrow again played the role of the behind-the-scenes strategist, but his team was ultimately outmatched and defeated, forcing him back into the shadows.
During this transformative storyline for Spider-Man, the vampiric entity morlun has returned to hunt and kill him. An associate of Morlun, a mysterious man named Dex, hires Jonas Harrow for a specific task: to secure a sample of Spider-Man's blood and analyze it. Dex wants to understand the source of Spider-Man's power to see if it can be replicated. Harrow, ever the amoral scientist, eagerly accepts the lucrative contract. This small but significant role places Harrow in the orbit of one of Spider-Man's most powerful cosmic foes and reaffirms his status as the underworld's foremost expert in superhuman biology and genetics.
This marks one of Harrow's most significant and darkest appearances. During Daredevil's tenure as the leader of The Hand, the criminal underworld of New York is in upheaval. Harrow is hired to create a new asset. He kidnaps a man and subjects him to horrific physical and psychological torture, rebuilding him as The Profile, a weaponized empath. When Moon Knight investigates, he is horrified to discover Harrow's methods. The confrontation that follows is not a typical superhero battle but a brutal, visceral beatdown. Believing it is the will of khonshu, Moon Knight pummels Harrow mercilessly, seemingly to death. This event was a major turning point for Moon Knight's character and served as a grim end for Harrow, showcasing the ultimate consequences of his life of crime.
While Jonas Harrow is not a multiverse-spanning character with numerous variants, he has appeared in some key adaptations outside of the main Earth-616 continuity.