Larva
Larvae are what most evil petitioners become when they first get to the lower planes. They are oversized worms or maggots with human heads. Stripped of their intelligence and memories, and not even considered among the ranks of the demons or devils, larvae are doomed to wriggle around in filth until they are promoted to a higher form or some imperceptive fiend steps on them.
They are actually a pretty hot commodity, since they can be used as ingredients in a wide variety of foods, potions and spells. They are used as a de facto currency across the lower planes. Night Hags currently hold a monopoly on the larva trade.