Elemental Rockshot

This ordinary-looking catapult stone can be fired from a scorpion or heavy mangonel. After it impacts (dealing damage as normal), elemental rockshot transforms into a Small earth elemental, attacking nearby enemies for 5 rounds before crumbling into dust.

Prerequisites: Craft Wondrous Item, summon monster III or summon nature’s ally II.

Cost to Create: 375 gp, 30 XP, 1 day.

Source: Heroes of Battle, page 136.