Their bodies till the gloam plains until they rot and fall apart, their wombs are used by men from the free who need inexpensive bastards to clean their kitchens and stables, their souls are toyed with by the rich until their amusement dies along with the slave. Slaves live to die, and no-one knows that better than the slaves themselves. Such is their despair they think not of revolt, but only of the release of the final obliteration. But the figurines are useless until they are given power. Each figurine is empowered by the soul of a man or women.
Slaves provide the soul.
Once a figurine is finished and purchased, then the buyer must also purchase a soul to inhabit the figurine and give it power. The younger the soul, the better. When the life has been obtained, then the soul must be released from the body. This is generally done in as long a religious ceremony as possible, presided over by as high a Priest as possible, and with the most possible enjoyment by the onlookers. The soul can live in a bronze figurine for many centuries before its potency fades and it is cast out as scrap metal to be melted down and re-soulled.