You start up the long spiral staircase. It comes out in a
small round room, from which you can see quite a distance in
all directions through the slit windows. You can imagine archers
standing in those windows and defending the castle before it
was ruined. A ratty and moth-eaten old tapestry still hangs
on one wall, depicting a hunting scene with lots of hounds and
people riding horses, all chasing a white stag. You see nothing
else of interest, though.
The staircase leads upward to another floor, so you begin to
follow it.
You've only gone around the spiral a couple of times when you
notice that the air feels colder. Around another turn, and you
stand face-to-face with a ghost!