A Marvel Comics
character. The being that came to be known as Man-Thing was originally a scientist
named Ted Sallis. Sallis was working in a secret government lab in the Everglades
to recreate the "Super Soldier" serum
that, back in World War II, gave Captain America
his mighty powers before its formula was lost. When spies attempted to steal the new formula Sallis injected himself with the only existing sample (of course) and promptly got himself into a car wreck that hurled him into the Florida swamp
. There the serum reacted violently with the living organisms in the swamp, destroying his rational mind and converting his body to a huge, monstrous mass of swamp muck and weeds.
Man-Thing is incredibly strong, and nearly invulnerable as his viscous consistency causes punches and projectiles to pass through him. He can even ooze through nets, fences, and jail cell bars and re-form on the other side. Though he does not think, he is a powerful empath and is drawn to emotions. Mild emotions detected in the vicinity of his swampy home draw him out to investigate; violent emotions actually cause him physical pain which he will attempt to end by destroying the source of the emotions. The presence of these emotions causes him to exude sulphuric acid from his body. Thus his tag line: "He who knows fear BURNS at the Man-Thing's touch!" When the target has either calmed down (not an easy thing when a swamp monster is burning you with acid) or died, Man-Thing's body produces a mucus that neutralizes the acid.
The swamp where Man-Thing lives is the site of an interdimensional gateway called the Nexus of All Realities, of which Man-Thing is the guardian.