Plasma leeches were a widespread species of spaceborne parasites. They spent their entire lifecycle attached to the surfaces of spacecraft, subsisting on plasma and similar energy sources that naturally radiated from such craft. Over millennia of space travel, they spread from Wol Cabassh to nearly every corner of the galaxy.
Plasma leeches were close biological relatives of the sentient Wol Cabasshite species.
Sources
"The Art of Revenge of the Sith" — Star Wars Insider 83–85
Wol Cabasshite in the Databank (original site is defunct)
