Bruise-leech Crawler
this unusual species of leech was native to the planet Nelvaan. It was named for the way it left behind a discolored bruise when it moved across flesh, drawing the blood it needed to survive. The Nelvaanian people used bruise-leech crawlers in certain rites and ceremonies, placing several crawlers on the flesh of individuals who were to be tested for inner strength and integrity. If the individual was worthy enough, they would be able to withstand the pains of the bruise-leech crawlers' bite, emerging from the ritual which unusual patterns of bruises etched on their skin.