1st app- Savage Tales #1
Ted Sallis first came to prominence in government circles as the chief chemist working on "Project Sulfur," a U.S. Army research program aimed at developing a means to survive bio-chemical warfare. Sallis developed "Serum SO-2,' which would have succeeded in immunizing human beings to all toxic biochemicals, but the mutagenic effects of the serum would have transformed people into monsters. The serum was never put into production.
After Project Sulfur was shut down, Sallis was reassigned to "Project Gladiator," a research program under the auspices of SHIELD, which was aimed at recreating the lost "super-soldier" serum that had spawned Captain America during World War II. Working separately from his colleagues, who included Drs. Wilma Calvin and Barbara Morse (later to be known as Mockingbird), Sallis evidently attempted to use a modified version of his SO-2 formula as the basis for a new super-soldier serum. He was close to success when he was betrayed into the hands of the subversive Advanced Idea Mechanics by his wife, Ellen.
Perhaps already suspecting betrayal, Sallis had earlier destroyed his notes. To guarantee that the secret would not fall into AIM's hands, Sallis injected himself with the only existing sample of his modified Super Soldier serum, and fled into the nearby swamp. Sallis should have died, but over the course of several hours, mystical forces combined with chemical science to transform him into the monstrous, misshapen creature who would be dubbed the Man-Thing. The substance of Sallis's body was eaten away and replaced by vegetable matter. Though he mimics the form of humanity to a large extent, he can no longer be considered human. Though he retains Ted Sallis's soul, and rudimentary vestiges of Sallis's intellect, he cannot be said to be intelligent in any meaningful sense.
Since the time of his creation, the Man-Thing has served as the guardian of the "nexus of realities," an interdimensional focal point which has manifested itself in the middle of the Man-Thing's swamp. Though the Man-Thing's adventures have occasionally drawn him away from the swamp, he has always returned, and it is said that he is destined to remain the guardian of the nexus on this plane of existence for as long as the nexus continues to manifest itself in this reality.