From the introduction: House of the Undying Sun is intended for four characters with an average party level (APL) of 6. Characters who complete this adventure should earn enough experience to reach halfway to 7th-level. A terrible sandstorm has isolated the desert fortress of Nazzet-Tukar. 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.