Thanks! The shadows are basically ghosts that have managed to take on physical forms (though hardly anyone is aware of the fact) and people avoid them at all costs because they can be dangerous. Ron had an unpleasant encounter with one when he was a child, which is how he lost his arm. Despite the incident, he became even more interested in the shadows and even went out looking for them, which earned him a reputation as a bit of a nutjob. As an adult, he lives in the woods by himself and spends time with the shadows, who are accustomed to him and don't give him any trouble. His shadowy arm is one that they made for him. There's lots more to it but it sounds so convoluted when I type it out haha!