From the introduction: The Spreading Corruption is intended for four characters with an average party level (APL) of 3. Characters who complete this adventure should earn enough experience to reach halfway to 4th-level. A corrupted druid's grove has mutated the local flora and they're now attacking passersby. 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.