Binary system which periodically (~20 year cycle) has especially high and low radiation periods.

The third planet from the major sun is marginally habitable to folk such as the Misfits, and has a diverse, if exotic, native ecosystem including giant clam monsters and presentient lizards.

The second planet from the major sun has a surface gravity of 2-3 times greater than normal for Misfit-type sophonts. It also has rich mineral and gem deposits. It also has a very thick corrosive atmosphere with a run away greenhouse effect.