The Mutants are a street gang whose criminal activity took place in Gotham City.
They are an antagonist faction in the Smallville Season 11 comics appearing in "Effigy" and "Lantern".
In Gotham City, a member of the Mutant street gang raced through the sewer on a motorcycle, fleeing from a robbery. When suddenly an armored arm reached 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 called to Nightwing for a report. The sidekick quips about using the handlebars from another motorcycle as she took out two more Mutants.
However several were savagely murdered by a mysterious creature.
Batman and Nightwing were fighting members of the Mutants when suddenly the sidekick noticed a bright yellow 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 and the heroes followed.