Arkanian Offshoots refer to any offshoot of the Arkanian race who were bred for a specific purpose, such as laboring in the gem mines. They are mixed-blood hybrids, with different traits that would make them perfect workers for whatever task any lazy pure-blood Arkanian simply didn't want to do.
In a rare example of good translation, they are nammed in the French version of the comic the Arkanian Scions.
Well, that translation is a perfect definition, as the Offshoots are descendents of pure-blood Arkanians, though they were initially created through genetic engineering. The creation of this race, and the treatment of them by the pure-bloods is quite... questionable. The Offshoots were essentially bred as a sort of slave labor and they weren't treated as highly as any pure-blood Arkanian, and efforts had been made by the Arkanians to eradicate this race by means of virulent plagues designed only to target the Offshoots. They were seen as a commodity, not living beings.
It would had made more sense if they were made deliberatly stronger and less inteligent but whatever. Or they could have hands that look like showels like the Kamnoan creations on Subterrel.
Arkanians aren't very creative, it seems. Those ugly beings with the too-white skin and the too-straight teeth.