RUM MUTINY -If cast on a fleet carrying rum, the crew consumes the rum and abandons the ship when they reach the next port. Target player gets no money for the emptied barrels of rum and has to hire a new crew.
you could possibly make it general or add potentially make it formula based so it functions based on the number of crew, amount of rum, and travel time. So target player may have a partial or total loss

uncommon
4 turns
target fleet
instant

target fleet loses all rum cargo and 90% of crew If rum is the cargo
crew does not depart until ship reaches port

if formula based
rum / crew x hours = % of rum drank and crew lost

Sir Henry Morgan does not approve..

Too complicated for such a low usage voodoo.

I'm flexible on attributes,
it would be much less complicated and easier to implement without the formula basis.

basically a variation of rotten food
just rum on board equals loss of rum and crew for the trip would be a lot more simple.

It could really jam someone up if you had a lot of them because fleets would be waiting in port with no crew.
Would need to be rare and cost more turns to reduce the possibility of mass usage against a large trade fleet.