When freed, Laurentius talks about "she who wants to eat her".
The general belief is that it is Maneater Mildred, given her name and garb, or the butcher that ambushes the player upon approaching Laurentius (it has been confirmed that the butchers were female despite their looks), but there is another theory.
There's nothing really that suggests the butchers do anything other than cut meat.
Given what Laurentius says, it seems the butchers chop up their victims and prepare their flesh for consumption. But if the butchers don't eat it themselves, who are they feeding it to?
Directly behind the first butcher, cutting meat at a table, is a hidden hole in the ground that leads to the area with the giant undead rat.
The butchers are feeding the giant rat, that's why it's so huge. It is already known that rats eat human corpses (which is why they sometimes drop humanity). The butchers kill hapless adventures, chop them up into little bits, and then toss their bodies down the chute, where the rat eats them.
To support this theory, when landing from the hole, the player lands on a pile of human remains.