Elemental Gem

You shout the name of an elemental lord and dash this glassy gem against a hard surface to activate it. It cracks open, casting a 5th-rank Summon Elemental spell to summon forth an elemental you control as long as you spend an action each round to Sustain the Activation.

This gem comes in four varieties: transparent for a living whirlwind, light brown for a living landslide, reddish orange for a living wildfire, and blue-green for a living waterfall.