Often PCs get on the wrong side of powerful users of magic or break into enchanted tombs, either may get them on the wrong side of a curse.
A town has a festival every year in the dead of winter. The festival of birds. The towns folk dress in feathery robes and beaked masks and dance and frolic in the belief that the changes of the seasons are controlled by the presence of birds. According to tradition, the festival tricks Spring into coming early because the birds have returned.