Freon was the only female member of the Terrific Trio.
History
Mary Michaels was Mike Morgan's fiancée until the day she was exposed to the radiation that turned her into a gaseous, freezing being. Together with her teammates, Mary adopted a new moniker and joined the government-sponsored team, the "Terrific Trio ". When the Trio learned that Dr. Hodges was behind the accident, in an attempt to pry Mary from Morgan, Freon spurned him and the team decided to punish him accordingly. At that point, Batman engaged the team and activated a ventilation system, which pulled Freon in, seemingly disassembling her, though, given her gaseous nature, she may have survived and escaped.
Powers and abilities
Freon was able to fly, had a freezing touch and could shoot ice blasts.
Background information
Freon seems to be based on the Fantastic Four member Invisible Woman. She also seems to be the opposite of her counterpart's brother, fellow teammate the Human Torch, seeing as he can fly and has fire-based powers. Freon's name is based on Freon, a trademarked name used by the Chemours Company as a generic descriptor for a group of chemical gasses previously used as refrigerants. The use of many Freon gasses was banned in 1987, due to their effects on the ozone layer.
Appearance
Batman Beyond
"Heroes"