Well, I think Skaarj had their homeworld, planet Skraath in ancient times. But they haven't got it now, it became uninhabitable because of the skaarj-mercenary wars. Skaarj conquered the mercenary homeworld, but their enemies were an advanced race then, and from space bases they massed a great fleet and stroke back hard. In a sudden and unwaited attack, mercenary capital ships jumped out from hyperspace and started bombing the surface with tarydium-based nuclear weapons. Billions of skaarj and the Great Council of the Thirty Old Queens died (I try to imagine their society similar to dark elves' in Menzoberranzan: clans founded by strong queens fighting constantly with each other, but against external enemies, they cooperate effectively most times), and a nuclear winter came, conditions that are too harsh even for this highly accomodable race. Now Skraath is a penalty colony for their most dangerous criminals: first of all, rebels.
It was a suicide mission: the skaarj space defence finally eliminated the mercenaries, forcing them to became the nomads, pirates and unreliable salesmen of the Galaxy. Losing Skraath wasn't a fatal loss for skaarj anyway (despite demoralized them a bit), as they still dominate hundreds of planetary systems.
