They're doing human sacrifices to influence fate and are bounding the ghosts resentments/heaven wrath to him so that they can escape consequences.
They made him an evil energy recipient or something and make him think it's because of the circumstances of his birth to bind him to the estate (the classic "nobody but us could put up with you so don't try to leave" manipulation).
That's what I understood of the story so far at least.
I'm wondering if they drugged Chanrang to make him look sick to push Cheongdo to ask for the ritual.
let em cook ,, someone who rarely gets sick falling sick under evil circumstances is a bit suspicious
we'll have to see abt the making chanran sick part but I thought it's coz his heart hurt and he was in the rain after that conversation with cheongdo where cheongdo was pushing him away, I think lovesickness made sunshine boi sick coz of the stress
Why the fuck they treat him like that