The group of costumed criminals who would become the Gang originally would grow up with each other in the poverty of South Side of Chicago. Each one would swear to get out of their dismal living conditions and become wealthy beyond their dreams. Their frustrations and resentment would fuel their developing talents, working hard and reaching peak human conditions rivaling meta-humans. Deciding to come up with costumed identity's they took a lifelong neighborhood nickname, the Gang was than born. Connecting with the criminal underworld the Gang would take assignments from the secretive organization named the Council.
The gang would be led by a statuesque blond woman named the Brains, not a meta-human, however she had a genius level I.Q allowing her to be a brilliant strategist. Kong would be the muscles of the Gang, with incredible strength and stamina he became the brute of the group but would be no match for Supergirl. Ms.Mesmer developed near supernatural mass hypnosis abilities having grown to fine tune her skills with the aid of the specially patterned lights coming from the disk on her chest. The last of the quartet would be Bulldozer who would use his immense bulk to plow his opponents down, he also was of meta-human level strength and stamina. Both men would wear bulletproof costumes with Bulldozor wearing a special helmet.
The Gang went up against Supergirl at two occasions but were beat each time, however Brains escaped being captured and has been at large since. She would return to attack Supergirl again as Matrix-Prime, a robotic version.
After the crisis of the infinity earths and with the reboot of the continuity, the history of the pre-Crisis Supergirl was erased and several of their adventures were rewritten as starring by Power Girl. The destiny of the gang was unknown until the JLA 28, when the disgraced Triumph tried to sell them memorabilia from the destroyed JLA satellite. Unimpressed, the gang mocked Triumph and tried to kill him but the tables were turned around when the desperate fallen hero invoked the blue djinn LKZ, who effortless killed the Gang members. It has been confirmed Brains, Bulldozer, and Kong were slain by LKZ. Ms. Mesmer remains alive as of this writing.
The full Gang would appear a last time as background villians who were easily defeated by a newly debuted Supergirl. If these are new members taken over old identities or a rebooted version of the old ones, is unknown.