The Mutants are a street gang whose criminal activity takes place in Gotham City and an antagonist faction in the Smallville Season 11 comics appearing in "Effigy" and "Lantern".
In Gotham City, a member of the Mutant's street gang races through a sewer on a motorcycle, fleeing from a robbery. When suddenly an armored arm reaches out and knocks the gang member off his bike. He cowers as he finds himself before Bruce.
Using a small Bat-tazer, Batman incapacitates the gang member and calls to Nightwing for a report. The sidekick quips about using the handlebars from another motorcycle as she takes out two more Mutants.
Batman and Nightwing were fighting members of the Mutants when suddenly the sidekick noticed a yellow bright light in the sky. Nightwing thought it was a storm, but Batman knew it was not. The Mutants then made a beeline towards Arkham Asylum with the heroes following.