“ The PC's end up in a strange world where the very rocks are made of gold and jewels.As such gold and jewels is worth very little, but the iron in their swords and belt buckles is suddenly worth a LOT.”
“ A large river that is continuously covered in a thick layer of fog. There will be either a rope ferry to get across or possibly a boat that is rowed across by worshippers of the water elementals. It is very thick fog to the point where it even muffles voices even at close range and visibility even beyond a foot is almost impossible.”
“ A casual remark by one of the party about something met on a previous adventure leads to a summons to and grilling by the Mages' Guild (or equivalent), probably resulting in an expedition back to that area to recover the things for study by the Guild. The party's presence will be 'requested' for this expedition.”