Returning coin of avarice
Cursed platinum coin that links itself to whomever picks it up (it takes 10d6 days between linking to its victim).
Everytime it is used in a transaction it will return to linked entity within 1d10 minutes with upto d4 gold coins.
Everyone who sees this coin will try (by whatever means possible) to acquire it from the linked entity, (whether by stealing, transaction, murder, etc) until they become the linked entity.
The linked entity will become unwilling to part with any currency they possess, in order to make a transaction there must be an opposed persuasion check (persuasion vs insight) in which the linked entity fails the opposed check.