Elemental Gem
Item 10ConjurationConsumableMagicalSource Core Rulebook pg. 570 2.0Price 200 gp
Activate 
command, Interact
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-level
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.