Gaia Drums are really nice spellcasting Items... at least, unless you get unlucky. Each time you use a Gaia Drum, it casts Earthquake 10 on your foes, but also has a 1 in 20 chance of being lost. Nothing is actually weak against Matter, the elemental type of the Ability, but it's still a nice option to have. You can buy these in the town inside the cave on the Tropical Island cave if you want more.