Unless things go insane in the late game the whole chattel monster slavery thing seems more like it was a marketing gag meant to be shocking. You put mons to work chopping wood and mining and shit but they have a happiness meter that drains and you need to provide them with good food and rest facilities to maintain happiness or they'll just fuck off and stop working
I have this one faggot Tombat who spends more time in the hot tub than he does actually mining