SKULL is a criminal organization originally operated in Metropolis.
They were a loose-knit organized group of common criminals who banded together in an effort to compete with The 100. After the Atomic Skull began working with SKULL and provided them with S.T.A.R. Labs tech, they were able to achieve notoriety and recruit other brilliant scientists into their syndicate. SKULL was responsible for numerous crimes in and around Metropolis and was put out of business time and again by Superman.
Eventually, the Atomic Skull left SKULL to work solo and the group temporarily disbanded. A group that called itself the Skeleton Gang was organized with the remaining members of SKULL. Their objective was to steal the valuable Egyptian artifacts on display at the Metropolitan Museum of History. Once again they were stopped by Superman Since then SKULL has been reorganized by person or persons unknown with the intent to go national with branches across the United States. Each branch has a separate specialty such as a space and nuclear research near Houston and shipping off the Florida coast. Few are aware of SKULL's return and their encounters with superheroes were limited. They also briefly clashed with the Kobra Cult.