Stardoc

After regaining her memories and saving the reptilian Hsktskt from a devastating plague, Dr. Cherijo Torin faces a different kind of epidemic—a mysterious black crystal spreading like cancer throughout the galaxy. A mercenary claiming to have information on the crystal’s origins leads Cherijo and her husband Duncan Reever to the planet Trellus, and maroons them there.
 
Trellus is a world under quarantine. Its colonists exhibit excessive paranoia and anger, taking out their frustrations in the Omega Dome in simulated combat against battle drones. But someone—or something—is killing victims outside the arena, leaving only their skins behind. Cherijo believes the black crystal infection is responsible for this horror—and that someone deliberately triggered the outbreak.