Brainstorming for my villain evil plan
Hello, fellow writers! I'm Italian, so I apologize for every mistake in my post in advance.
As per my title, I'm working on a big plot point, but I don't know enough ✨science✨ to be sure I'm doing things right. I'm too much of a Literature student to know STEM.
But, silly me, I decided to write a historical fantasy with a bit of steampunk, and one of the main charachters is a doctor. Smart move, eh?
Anyway. this is the thing: the villain in my novel is a dryad who is posing as Goddes for a very twisted cult. It's a very secluded community in a small village, with very strict rules for its members. One of those rules is that only girls can serve the Goddes. They are personally chosen by the Goddes as soon as they are born and raised in a secluded place. Their appearence changes so the family will never know who is their daughter, and they are named after the flower they resemble.
The girls have a lot of strict rules to follow (how much and what they can eat, how they can spend their time, where they can go, how they can dress, and so on), and they are mostly brainwashed by the adults who raise them. And to be extra-sure that the girls don't disobay, the Goddess writes on their backs a very twisted magic that works as a list of rules to follow. If they disobey, the magic makes them sick or (in the worst case scenario) punishes them killing innocents around them.
I'm not going too deep into this because is not the point.
The thing is, the dryad wants to escape the tree, because she was sealed hundreds of hears ago into it, and she's not happy about it. So she's harvesting these girls to breed The Ultimate Vessel. Until now, when she possesses a girl, the body can't accept her for long, because she's a plant and they are humans. So she's trying to make the girls the most plant-like she can.
And here is the thing.
When the girls reach adulthood (21 years old), they have this ritual and start and phisically change. Their skin resemble a tree, their hair look like leaves, and so they leave their flower name for a tree name. This is on the surface. On the deeper level, they lose attachement for the other girls (even if they loved their sisters up to two minutes ago) and start to live for the Goddess and the goddess only.
Now, my main characters (the protagonist is one of the girls, and she has the help of this doctor who escaped the cult many years before her) had the chance to capture one of these tree-women, and they try to study her body because they want to reverse the process and save her. They have access to medicine knowledge and equipment from XIX century (the novel is set in 1851, so I'd stretch the steampunk up to a few decades later), blood magic (for healing), and maybe a bit of alchemy.
I need a bit of help to make this sound plausible, because I have a few ideas on what the dryad may have done to this woman, but I don't know if this can work.
To be crystal clear, the goddess doesn't care if the woman has health problem because of her experiments. She wants the vessel, and if one or many suffer in the process, so be it.
So I thought that she messes up with all she can. She turns off the reproductive system, because these women will never use it, and plants don't reproduce like mammals. She destroys lungs, because plants uses leaves to breathe. Under the barks-skin, probably there is no more blood, but... sap? (Sorry, I'm not sure if that's the right word.)
Sadly, I can't go further, so I'd really appreciate your help.