(maybe a pretty sensitive topic below, but i tried to tone it down so it could be more appropriate) One of my side character would be a woman who was sold by her own father to pay his debts to a mafia boss. Then, the boss kept her as a captive in his basement for 13 years and made her his 'personal slave'. One day, this woman saw the mafia boss fell from the stair that connects the basement to the upper level, full of bloods and wounds. Then MC come and slaughtered the mafia boss, but before he died, he begged for mercy by offering the woman as the price for his freedom. MC then broke the chains that restrained her and gave her the option to start a new life by leaving the place, but the woman decided to join MC's cult as a payback instead. In the story, she would be a sniper or the team because how she spent 13 years without sunlight (she was 22 when she met MC for the first time, so her father sold her when she was 9. Also there's a 5 year time gap between their first meeting and the main event of the story). The question is, is it possible that spending 13 years in a basement without a slightest sight of sunlight would enchance her eyesight, and thus making her a better sniper? Or instead, will it make her eyesight worse because her eyes don't adapt to sunlight like how others should?
I think you need to focus way more on the mental effects than the eyesight. Stockholm Syndrome would be very real here, to the point she may attack the MC with no regards to her life.
She is thankful that MC saved her from that hell hole to the point where she could undoubtedly take a bullet for him. She was used as a toy for years and someone saved her, embraced her as a human being, and never even forced her to join him. She joined the team with her own consent, of course with MC's influences, but he gave her the choice to not join. Yes, definitely there will be mental effects on her. She had a hard time adjusting herself with the world after the 13 years skip, fear towards men, and also PTSD everytime she's in a closed area or when she have a mission in a brothel. MC managed to made her feel better, give her the ability to catch up with the society, and also cured her trauma towards men (she have a male love interest in the story, and as a general of the cult, she interacts with a lot of men in the cult with no problem). But yeah, MC can't cure her PTSD because he struggled with his own for years. If he could others', he would heal his. And i'm pretty sure that she won't develop a Stockholm Syndrome after all that. The only thing she develops during those years is hatred towards everyone who did her wrong.
Ah, bats and moles. How can i don't think about this. Thanks for this, now i could come up with a solution to fix her eyesight. Wait, i forgot something. I forgot to mention that the basement wasn't totally dark. It wasn't exposed by sunlight, sure, but there's still lamps and aromatic candles in the room to light things up (how would they do the 'thing' without proper lights?). Would that still affect her eyesight that bad?
Vitamin d deficiency can be cured through a proper diet. However the brain needs sunlight specifically in order to maintain proper sleep schedules and serotonin levels. I don't know about the eyesight.
Also, watch out for physical fitness. 13 years in a room without exercise is bound to atrophy muscles. I don't know how realistic it would be to start regenerating muscles at 22 to the point where she could be considered for a sniper's position. Also, psychological assessment. You are not getting into a sniper's MOS if there's even the slightest hint of mental instability. And not with PTSD. No chance. Sorry, but I don't find her eventual position realistic.
Even if she didn't lose her eyesight, I would think she'd be overly sensitive to light. Like the Morlocks in The Time Machine. And depression levels might be through the roof. I know more than a few people who can barely get through Canada's overcast winter let alone no light.
But she wouldn't get a deficiency ever if given a diet to compensate for lack of sunlight. As far as I'm aware. (I'm just going off Google.)
Something nobody's mentioned so far is that, eyesight or not, she'd need a hell of a lot of training after being rescued to actually become a sniper - just having good eyesight (if we consider the unrealistic possibility that some kind of condition down there gave her that) she would have to practice and train for years to be a good sniper. You may already have considered that by just in case.
She did. When the person that MC saved chose to join him instead of a new independent life, he'd train them depending on what kind of weapon they want to use. And since there are 5 years gap between their first meeting and the main event, i could say that she improved a lot.
MC is an international fugitive so he wont care much about MOS. He is also a scientist, so i guess i could just make him 'cure' her body with his stuffs. But yeah, maybe i overlooked her mental state throughout writing her. I'll try to see what i could fix with that, maybe i will just remove the PTSD and replace it with something less.
So your rescuer MC is: 1. An international fugitive 2. A scientist who's developed a cure for... weakness? 3. An expert in any weapon his team want to use, and able to train them all individually in 5 years 4. Going to break your trapped character out of her confinement without any help from all these people he's trained?
1. Yes. His whole goal is to kill anyone he deemed evil, including many important politicians. That is what made him a wanted man. 2. Definitely he won't cure her in a day or two. I will maybe write it as a therapy that took months before she could actually do something meaningful 3. Not all, but a lot of weaponry. And no, he won't train all those people only by himself. His cult is expanding throughout those 5 years, and he set his older members to train the new ones. Also, i already wrote how she was assisted in mental therapy and physical training by a more senior cult member - a man that she would fell in love and have relationship with, when she is finally able to accept a man in her life. 4. MC did a lot of things for her, but the man in point 3 was closer. During those times, MC can't really get too personal to the new recruits since he is still busy building his cult. This is probably where i give a hint of how a cult member interacts with each other. Since they are all a broken and desperate person with a grim past, i suppose they should help each other out, and this side character will be accepted by the cult society regardless of what she went through. I know this looks confusing. I wrote a map to point out possible choices about characteristics of the cast, so it most likely would change if i feel that another option is better than current one.
I'm not necessarily saying that it's confusing, I'm say that your main character seems like the kind of man that can literally do everything - and if that's the case (it might not be, if I've misunderstood) then perhaps some of those characteristics should be reconsidered. All I was trying to say that up to this point, whenever anyone has pointed out a potential problem, your answer has been "the rescuer MC can do *this* to fix it". Hope this makes sense.
Characters who are good at everything are generally quite boring, imo. EDIT: @The Piper beat me to it.
This. And no, MC is not the 'capable of doing everything by himself' person. That is why he made a cult, not only to help them, but also to help him to move towards his goal. He is just a revolutionary man with a lot of advantages, but if not used correctly, his advantages would backfire on him or those he loves. But still, he is a godsend for most people he rescued, to the point where few of them considers him to be the new Messiah or something like that. Thank you for your feedback.