The Fog is a nanotech weapon invented by Dr. Serling Roquette.
The Fog was invented by Dr. Serling Roquette of Royal University in Star City. It was made from millions of microscopic robots that can not only destroy everything in their path, such as concrete, steel, flesh, and bone, but can also hack into any system and retain the information.
The League of Shadows captured Dr. Roquette and forced her to make the Fog for them. Though Red Arrow managed to rescue her from Infinity Island, the Fog was ready to be used. Roquette set about to create a virus that could shut the Fog down.
The League of Shadows first destroyed Miami Beach University as a test run, and later obtained vital information from STAR Labs in Philadelphia. The virus was uploaded before the Shadows could succeed with their second target, Wayne Tech. The Fog was destroyed.