Samuel Stearns was once an ordinary human being with average intelligence. A high school dropout, Sterns
worked for a chemical research plant in a menial capacity. While moving radioactive materials into an underground storage area, some of the
radioactive materials exploded, bombarding Sterns with gamma radiation. Sterns recovered, but found that the radiation had changed him from an ordinary human into a green-skinned,
super-intelligent criminal with an oversized brain housed in a towering cranium.
After a period of time the gamma radiation in his body began to wear off. At first the Leader attributed
his lapses in concentration to overworking his mind finding ways to defeat his greatest enemy (the Hulk). By the time the
Leader realised what was happening, much of the intelligence that could have solved his plight was gone and texts that were
once childs play to him were now hopelessly beyond him. In this period he made cash however he could by means fair or foul
until he managed to convince the Grey Hulk to help him regain his intelligence by promising him that he would be able to remain the Hulk full time
(instead of only at night).
Rick Jones had been afflicted with a Hulk-like condition and the Hulk (using Bruce Banner's memories of gamma transfer)
devised a machine to transfer all of the gamma radiation from Rick Jones to the Leader. However, this time the mutagenic process
was slightly different resulting in a cranium that resembled an over-sized brain, rather than a towering forehead. He was
also a lighter shade of green. As a side note this transfer also created a psychic link between the Leader and Rick Jones.
At first after the transfer the Leader shared all Rick Jones' memories, but afterwards the link became stronger with the death
of Marlo Chandler.
The Leader learned from an alien race known as the Ovoids how to transfer his consciousness,
including his vast intellect, into other bodies. At sometime in the past, his body was destroyed and he simply occupied another
one. At present he has a body essentially the same as his original which has an appearance somewhere between his two former
gamma radiated bodies.