The game, was developed by California-based Cryptic Studios Inc, and published in April this year by South Korean firm NCsoft Corp.
Set in the aftermath of an alien invasion in a virtual world known as Paragon City, villains and mutants battle users in the guise of superheroes – guises that they design themselves from a huge array of features, costumes, characteristics and skills.
According to the Associated Press, Marvel Enterprises is concerned that this design feature allows subscribers to copy its comic book characters, thus infringing its trade marks, and potentially affecting its ability to licence the characters into other video games.
It has therefore sued, seeking damages and an injunction, on the grounds that the characters, while developed by subscribers to the game, are created on servers run by both NCSoft and Cryptic Studios.