Another cursed stone:
Stone of Heaviness
A stone of heaviness, if discovered, will seem to have the same properties as another beneficial magic stone such as a stone of warmth or coldness, and will act as such, but upon the second day its weight will increase to 1 stone (14 pounds or 6.35 kg). Thereafter, its weight will increase by another stone each day. Meanwhile, the beneficial properties will cease on the eighth day, although the weight will continue to increase daily until it reaches the maximum weight capable of being lifted by its possessor. Each day, the possessor will be notified by the referee that his or her encumbrance has increased by 140 coins (or whatever number of coins equals 1 stone in the campaign). A stone of heaviness may only be discarded with the casting of remove curse.
Like other magic stones, a stone of heaviness has no standard size, shape, or coloration, and will only activate when in close proximity to a living creature.