Engorgio

Engorgio is a charm that causes the target to swell (by adding the original size) per round. With enough time, this charm is strong enough to grow a pillow out of an iron vault. The target must be an object, unless you first succeed in a Constitution check. Then, and only then, can you attempt to engorge a creature (no bigger than yourself) to the point of explosion--in one round. The target can attempt a Strength saving throw, but will take 1d8 of force damage even if successful.

Example of swelling: 2 gallons of water become 4 gallons the next round, and 6 the following round. A 3 ft. boulder becomes a 6 ft. boulder the next round, and a 9 ft. boulder the following round.