Look for some clue on the 'thing', how's the attire, any scar, sort of that, then find information on it who's that guy, and what is it he wants.
Maybe you should also prepare some salt and a cross, or a silver stick, a metal bar, use everything on it, see what happens. And look out for any
clues on him.


....but i got amnesia and forgot almost all of what happened that month, but I think he's a
ghost.
Or you might have a brain tumor (but brain abnormalities usually aren't this specific) 