“ 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.”
“ In your world the pantheon is a rotating system of formerly human individuals. You have been selected for god-duty for the next 2,000 years. How are you going to get out of this?”