The dreamtrails

Wavesong (Obernewtyn chronicles, v.5) : Elspeth and the other Misfits successfully defend the Land against a Herder invasion, and in the process manage to take over Herder Island. The stone key (Obernewtyn chronicles, v.6) : Elspeth must find and stop the person infected with the plague before sickness -- and ultimately death -- threatens everyone in the Land.