Sound the Retreat With a handful of survivors from a Swarm invasion as passengers the heroes travel to a nearby colony world in search of safety. At the overburdened metropolis of New Grakka members of a movement who believe the Swarm are punishment for the systems sins are disrupting the militarys efforts to take in refugees. The heroes must stop these fanatics as well as clear out a series of caverns beneath the city that could provide shelter and protection should the Swarm attack this planet