It depends. As the author, you must always make the decision that fits with and enriches the story. Obviously, J. K. Rowling didn't feel like she...
What makes him unsettling? Is it his mannerisms, speech, general presence? Try to give the other characters a reason to feel uncomfortable, noting...
In this case, the thief is the original instigator. By your description, he pops in, steals something, and then leaves for the other world. He...
Hello there. I am Shard, and apparently bad at writing. I came here to make myself better. So yeah, that's pretty much it.
Separate names with a comma.