This will appear as a silver ring of great craftsmanship. Magical testing will reveal it to have the power to sustain the wearer without food or drink for an indefinite period of time.
The curse has a cumulative 05% chance per day of taking hold (GM rolls once per day), whereupon it will start having the opposite effect. The wearer starts becoming very hungry and thirsty, and must continually consume food, or begin losing 1 HP each of Strength and Constitution per minute! They will die if either of these Statistics reaches 0. At most, they'll be able to go 1 minute per character level without consuming food, before they begin losing points. Eating like a glutton for one minute per lost point will return them to their normal Statistics.
A cursed wearer will have to eat and drink constantly, not even taking time out to sleep. They will gain no weight from all this food, and will even start losing it at a frightening speed, as they lose HP.
The victim is free of the curse if the ring is removed, though they will not be able to do so without a successful Remove Curse of high level. Severing the ring finger will also work, but in this case, the lost finger cannot be reattached or regenerated even by powerful magicks!
Optional: If normal food isn't available, the victim's companions might start to look appetizing!