Jackson Day was born in Smyrna, Delaware. An ordinary pharmaceutical factory worker, he was exposed to psychoactive chemicals from a fire. Thor rescued him from the fire, but he had already begun to mutate, causing Thor to go on a rampage just by his touch.
Day was soon transferred to the Avengers' mansion for treatment. He escaped, abandoning his wife, and became the head of the criminal Inner Circle. With the Inner Circle, he recruited people in financial straits, supplying financial assistance requiring the victims to commit crimes on his behalf.