Bombchu

Bombchus are a type of mobile explosive that travel along the ground until they either self-destruct or touch an object or enemy.
  As an action you can activate a Bombchu by setting it on the ground and letting it go. The Bombchu will move 30 feet in a straight line, or until it comes in contact with an object or creature, then it will explode. At the start of your next turn, if no objects or creatures have come in contact with the bombchu, it will continue for another 30 feet, or until it comes in contact with a creature or object, then explode.
  When a bombchu explodes, it does so in a 5 foot radius centred on itself. Each creature in the area must make a DC 10 Dexterity saving throw, taking 2d6 damage on a failed save or half that damage on a successful one. Half of the damage is thunder damage, and the other half is fire damage.