Kyle Nimbus, nicknamed The Mist by Cisco Ramon, was an assassin from the Darbinyan crime family. He was affected by the S.T.A.R. Labs particle accelerator the night he was supposed to be executed via gas chamber and gained the ability to transform himself into poisonous gas. He later became the first inmate of the makeshift particle accelerator prison under S.T.A.R. Labs. However, he, along with the rest of the imprisoned meta-humans, were eventually freed by Leonard Snart and Lisa Snart.