From the introduction: Beneath the City Streets is intended for four characters with an average party level (APL) of 4. Characters who complete this adventure should earn enough experience to reach halfway to 5th-level. Goblins have been erupting from the sewers and no one knows why or how they got there. This campaign takes place in Arden, although it can be set in your own world. Any party composition should be able to finish the adventure with intelligent play.