Dark Side of the Sun introduces an interesting new twist to the Opus setting which is sure to inject your campaign with some uniqueness. This is a very nonlinear format, so be prepared for that make-it-up-as-you-go-along element. Where possible we've tried to cover most eventualities.
Each Opus adventure highlights and introduces a different aspect of the Opus world. Dark Side of the Sun explores an historical aspect of Opus and is the first in the Chronicle series. Other sets include the Pantheon series (introducing one of the Opus religions) and the Locus series (focusing on an Opus location).