In appearance they are short, blank-eyed and bald with pale-skin. These vacant creatures are created to harvest fungi for the Demon Princes, and come in two varieties - Workers and Warriors. The two types are very much identical to each other, with the only point of distinction being the larger stature of the Warriors, who are also armed with weapons and dressed in Leather Armour.
Purpose of the Clones
Servants of the Demons of the Pit, the clones are created for a single vocation - to harvest some of the very mushrooms that they were created from. These mushrooms appeal to the eccentric palette of the Demon Princes, who, during their banquets in which all manner of ribald evil can be found, nevertheless make time to enjoy the delights of some species of Titan's fungi.
However, cultivating mushrooms is a tedious business. Indeed, this labour was deemed so dreary as to be beneath even lesser undead, while Demonspawn proved too erratic to reliably carry out the task. Thus, Clones were created to rear the mushrooms.
Clones actually occupy a level in the Pit's hierarchy - that of Sextus, aptly labelled "The Brainless Ones". The only creatures that rank beneath the clones are the formless Demonspawn. Clones and Clone Warriors are the only inhabitants of the Sextus tier of the Pit's hierarchy - presumably the procuring of the mushrooms is sufficiently important to the Demon Princes to warrant creation of a new rank.
However, the Clones have no other claim to importance. They are little more than shambling, droning things - what little dregs of consciousness they may have is bound up in sole concern with their appointed tasks. For the workers this means thinking about the status of their current crop, for the warriors it means the details of their security patrols. The Clones apparently have no instincts other than fulfilling their task. Workers in particular will not pay attention even if one of their number is suddenly killed.
Clones therefore require some oversight and supervision, and this mind-numbing job falls, almost invariably, to lesser Demons who are in poor standing or ill-favour with the powers of the Pit. These Demons, relegated and doomed to one of the humdrum fungus plantations found across on Titan, find themselves donning a Crown of Control to direct the Clones.
Crown of Control
A higher intelligence supervises the Clones by means of a golden crown. This headpiece provides a telepathic link between its wearer and the Clones, who will regard whoever bears the crown as their master. The Crown, once put on, cannot be removed except by one of the Greater Demons doing so, or by the death of the wearer. Placing the crown on one's head is a bad idea, as it carries with it the exact, unenviable fate of its former owner. The new owner will be telepathically linked to the Clones and will also find himself transforming into the creature that previously wore the crown. 
The giant mushrooms that the Clones have been seen to harvest can be potentially hazardous. The red topped ones are known to be very harmful if consumed, whereas the green topped ones have a salubrious effect and can restore lost strength. 
The Clones themselves are possibly formed from purple-topped mushrooms, as this type of mushroom has been found to sprout up from where the Clones bodies have dissolved into purple liquid after being slain.