Reddit mentions of DARKNESS WALKS: The Shadow People Among Us

You say that until tonight you haven't felt any ill intent from the entity. But that changed? From what I've heard there are essentially two 'types' of shadow being encounters- some are passive and seem more like typical ghosts, sometimes not noticing other people/surroundings, but sometimes they will focus on people and watch them. Then there are more malevolent ones- These entities seem to inspire very intense fear and act quite menacingly.

This is a strange-sounding question, but does your entity wear a hat?

You might want to check out this book. I haven't read it but I hear it's pretty good.

I don't know how you'd go about getting rid of the thing. I think I would try and ignore it for as long as I could, and maybe try burning some sage and performing an amateur house/room blessing if it got worse.

(*Quick edit because I just remembered something)- I did hear an interview with Jason Offutt, the author of that book. I remember him saying that when encountering the more malevolent 'type' of shadow person, people seemed to have success with prayer (if you believe in that sort of thing), laughing, and singing/whistling. It sounds like the expression of positive energy is what does the trick. I wish you luck!