The Iron Cluster is a collection of sub-sectors surrounding Tempest. They are colony worlds, but more militarized than the worlds in the Homestead Marches. Most are low population and undeveloped, but are able to rouse substantial militias or even have space fleets. They are currently struggling to hold back the green tide from the north, while at the same time contending with Eldar raids, the awakening Tomb Worlds.
At the heart of the Iron Cluster, Tempest rests. Though it is the most central, and the most politically relevant in the grander scale of the Pegasus Gulf, as a feudal world, Tempest contributes little to the Cluster economically or politically.