The slug will have to enter along the southern wall to see the woman, because there is a cloud bank between them. I can put the slug at 0N100E.
The slug hits (rolled 18), but does not do any damage (DR 4 or greater), so the harpoon does not stick in the woman.
Round 471: The woman gestures, and a bank of fog surrounds her. It is centered at 60N20E, has a twenty foot radius, and it uniformly twenty feet high. (What is it about this arena that invites these clouds? Maybe it is the extreme chaos working.)