There are only a few ways of dealing with these entities, all of which require some knowledge of magical practices. One of the best ways of dealing with them is to remember a very happy moment when you feel a kind of tingling inside you rise up in response to this memory hold onto it and try to focus it to a single point on your body. Try and visualize it as pure white light and then release it at the shadowin. It's the most reliable way of getting rid of them for good unless you are capable of shamanic magic and can consume them. If you are not capable of doing either of these things get holy water, blessed salt, or make the ghost powder listed under the ghost section and keep it on hand if you are having trouble with these entities. A small dash of holy water should dispel the creature while the ghost powder will disperse it and prevent it from coming near you.
Shadowin are known by many names across many places, shadow people, shadows, shadow men are all names for these creatures of pure shadow. It is unclear as to where they originated but I do know regardless of where they came from originally they can reproduce by gathering negative energy to them. Such energy is generated from fear, anxiety, despair, and rage. These creatures feed off of this energy and take many different forms ranging from small insect like varieties to large hulking humanoid ones. The most common variety seen is the man in the hat and the cloaked figure, though do not be surprised if it changes forms. They stick close to people which generate the energy they need to sustain themselves on though will actively seek out those which are bright beacons of positive energy in an attempt to snuff out their light which can be deadly to them.