Ted Sallis, a native of Omaha, Nebraska, is a biochemist working in the Everglades who develops a "miracle drug" later defined as an attempt at recreating the "super-soldier serum" that created Captain America. Betrayed by his lover, Ellen Brandt, Sallis flees from agents from Advanced Idea Mechanics (A.I.M), who covet his formula and research. He injects himself with the serum, but after crashing in a swamp and apparently drowning is transformed into a swamp creature through a combination of his formula and, as later explained, magical forces extant in the area. Sallis' mind was apparently extinguished, although on rare occasions he could briefly return to consciousness within his monstrous form, and even to his human form Sallis' assistant was an elderly African-American scientist, Dr. Wilma Calvin.

Visitors to the swamp soon discovered it was a place of mystical properties known as the "Nexus of all Realities", and Man-Thing found himself facing demons, ghosts, and time-traveling warriors, while continuing to encounter such non-supernatural antagonists as rapacious land developers, fascist vigilantes, and common criminals. Regular visitors included the demon Thog the Nether-Spawn, the benevolent Dakihm The Enchanter, Howard The Duck, and several humans, including members of the Cult of Zhered-Na (led by Jennifer Kale's father, Joshua. Developer Franklin Armstrong Schist attempted to build an airport in Citrusville. Dakimh declares Man-Thing, Jennifer, Korrek The Barbarian, Warrior Prince of Katharta, and Howard are, with him, the chosen five needed to defeat Thog.

Twenty-something radio DJ Richard Rory moves to Citrusville, and nurse Ruth Hart, become involved in defending Man-Thing from Schist's attempts to destroy the creature. Rory in particular formed a bond with Man-Thing, while Hart left Rory for Hell's Kitchen, New York City.

In Man-Thing #7, reality set in and the energy crisis prevented F.A. Schist from completing his airport. The reason for the airport was then revealed: Schist wanted to find the Fountain of Youth. Unfortunately, he learned the hard way that the desired effects of the fountain's water come from bathing in it, not drinking it, and with a newly fragile body, was done in by Man-Thing.

Gerber also wrote five longer issues of a parallel series, Giant-Size Man-Thing, whose unintentional double entendre title became a common joke among comics readers (a "giant-size" comic is one with more pages than a standard comic book). The first issue introduced the Cult of Entropy, who would later be foes of the Incredible Hulk and Howard the Duck, even reaching the latter's newspaper strip. In the second issue, Schist's widow and daughter arrange to have the Man-Thing captured, but he escapes and runs amok in Manhattan. The third issue featured the death of Dakimh's physical form, though his spirit would continue to appear, while the fourth began the solo adventures of Howard the Duck. In the fifth issue, we see that Ted Sallis had prior knowledge of his future as Man-Thing from a fortune teller, who outraged him rather than making him pay heed.

In one story (#13–14), an astral pirate ship headed by Captain Fate, ended up in the Nexus. A scientist, Dr. Maura Spinner, was the reincarnation of a pirate queen and both were linked with a satyr named Khordes. In a controversial ending which Gerber expressed regrets about having written, Spinner stayed with Khordes.

Soon, Gerber was delving into Ted Sallis's past. In a text story in Monsters Unleashed #8 and #9, Sallis was revealed to have slept with an underage girl, whose father sought to kill the current occupant of his shack. In Daredevil #108, Gerber introduced Foggy Nelson's sister Candace, who was being harassed over research she was doing at Empire State University. In issue #113, this was revealed to be the Sallis Papers, research that could have turned the human race into smog-breathing monsters and allow industry to proceed unchecked. In Man-Thing #15, we are introduced to Sainte-Cloud, a young woman who helped Sallis decide to abandon the project. Sometimes this has been erroneously cited as the project that created Man-Thing, though it is made clear in the stories that this is an earlier project.

The final arc of the Gerber series (16, GS4, 17-22) dealt with a hypermasculine laborer named Sorensen forced into retirement at age 65. He went on a rampage as a Mad Viking, killed his daughter Astrid's artist boyfriend, and allied himself with Olivia Selby, who led a book burning riot at Citrusville High School, leading to the slaughter of several teachers. Man-Thing's involvement led to him being dumped in the local sewage treatment plant, which only increased his ability to leave the swamp, while Richard Rory got fired by the local radio station for speaking out against the book burning on air. Rory attempted to leave for Atlanta, and Man-Thing and Carol Selby, Olivia's daughter, demanded to go with him. In Atlanta, they met Robert Nicolle, a man with neither feeling nor physical sensation, who appeared as the costumed criminal the Scavenger, whose sister, Dani Nicolle, has her sensations on overload and must project them into objects called Nightmare Boxes.

A scientist, Dr. Oheimer, attempted to restore Ted Sallis's mind, now scattered about in ganglia throughout Man-Thing's body. A love triangle then took Man-Thing to the Himalayas. Chris Claremont, the writer by this point, introduced himself as a character in the final issue of Volume 2, as Steve Gerber had in the finale of Volume 1. Additionally, Claremont temporarily became the Man-Thing after being stabbed to death by a possessed Sheriff John Daltry. His and other characters' deaths were later resolved with the intervention of the War is Hell series lead, John Kowalski, now an aspect of Marvel Comics' manifestation of Death. Man-Thing later appeared briefly alongside the superhero Cyclops, aiding him in a battle against the supernatural villain D'Spayre.

Powers & Abilities

Man-Thing is a former scientist who became a nearly mindless mass of slime with no particular affinity to any living thing, but who nevertheless often becomes an accidental hero as it stumbles upon various crime and horror scenarios. It is able to sense human emotions, and is enraged by fear and automatically secretes a strong chemical corrosive; anyone feeling fear and clutched by the Man-Thing is prone to be burned (either chemically or mystically), hence the series' tag-line, "Whatever knows fear burns at the Man-Thing's touch." Though fear is understandably most people's response to the creature, typically only villains end up meeting an immolating death at its hands.

The Man-Thing possesses a variety of superhuman powers that are derived from the interaction of the scientific formula created by Ted Sallis and the mystical energies of the Nexus of Realities.

Man-Thing's superhuman strength varies considerably in his comic book appearances. Initially, the Man-Thing is only slightly stronger than Captain America, but in later appearances, the Man-Thing possesses sufficient superhuman strength to stand toe to toe with much stronger villains.

The Man-Thing's body is practically invulnerable to harm. Because his body is not entirely solid, but composed of the muck and vegetative matter of the swamp, fists, bullets, knives, energy blasts, etc. will either pass entirely through him or will harmlessly be lodged within his body. Even if a vast portion of the Man-Thing's body were to be ripped away or incinerated, he would be able to reorganize himself by drawing the necessary material from the surrounding vegetation.

The Man-Thing is also able to ooze his body through openings or around barriers that would seem too small for him to pass though. The smaller the opening, the longer it will take for him to reorganize his mass upon reaching the other side.

Unusual psychic and mystical forces react in what passes as the "brain" cells located throughout his body. These unique forces render the Man-Thing extremely sensitive to emotions. Emotions that are mild and generally considered positive arouse curiosity and the Man-Thing will sometimes observe from a distance. However, emotions that are often viewed as negative, such as violent emotions, rage, anger, hatred and fear, cause the Man-Thing great discomfort and might provoke him to attack. Once provoked into violent actions, his body secretes highly concentrated sulfuric acid that can burn human beings to ashes within a matter of seconds. Even individuals that have high levels of superhuman durability have proven unable to withstand this potent acid (except, perhaps the Hulk.) While the Man-Thing is devoid of violent emotions, his body produces a type of foamy, soapy mucus that neutralizes the acid.

The Man-Thing is dependent upon the swamp he inhabits for his continued survival. He is able to leave the swamp, and has done so on many occasions, sometimes for a considerable length of time. However, his body will slowly weaken and eventually lapse into dormancy if not returned to the swamp or exposed to clean water. His exposure to the Citrusville waste treatment plant greatly enhanced his ability to leave the swamp.

Spin-offs

Gerber introduced Howard the Duck in a Man-Thing story in Adventure into Fear #19. Howard, who was displaced from a planet of anthropomorphics in another dimension via the swamp's Nexus of All Realities, later acquired his own series.

The Foolkiller, a vigilante who used a ray-gun to disintegrate not only criminals but anyone he considered foolish, was introduced in issue #3 of this series, bent on slaying disc jockey Richard Rory, introduced in the previous issue. When Rory served time for trumped-up kidnapping charges, he accidentally created another Foolkiller when he revealed too much detail about the previous incarnation and the whereabouts of his gear. This Foolkiller became an occasional villain in other Marvel comics. Both Rory and this second Foolkiller, along with nurse Ruth Hart (who appeared in Man-Thing # 2-5) were supporting characters in Gerber's Omega the Unknown, while David Anthony Kraft made Rory a potential love interest for She-Hulk. A third version of the character, who was in internet communication with the second, starred in Gerber's 1990 Foolkiller miniseries.