Powers: Her mutant power is the ability to spread a chemical agent that turns to acid or anesthetic and can also use her mental powers to guide it where she wants and dissolve solid things. She is also believed to be a bookkeeper.
Bio: As part of the Resistants, she participates in the rescue of Mentallo from a vehicle conveying him to the superhuman prison the Vault. Mist Mistress personally melts part of the vehicle and the armor of a Guardsman found inside. Mentallo is taken to the Resistants' Death Valley hideout and officially joins the group.
Later, the Resistants attack a courtroom in Carson City, Nevada. They plan to free Quicksilver. They come into conflict with Captain America. Mist Mistress becomes frightened by the violence and retaliates with knock-out gas. This seems to work, but Captain America was simply faking it and knocks out Mist Mistress with his shield.
A Resistants-attended rally in Washington D.C. comes complete with a robot-duplicate of Magneto, controlled by the Machinesmith. Its use is to attract the attention of the real Magneto. Things go wrong and Captain America saves the group.
Mist Mistress loses her mutant powers after the M-Day (power-loss confirmed in New Avengers #18). Her powers, along with the mutant energies lost by so many others, form the murderous being called The Collective.