Exploding Gold Coins

A pouch contains 10 false gold coins. As an action, you may scatter up to 10 coins into an adjacent 5-ft square or throw the pouch up to 20 ft, scattering the coins in a 5-ft square where it lands. The first time a creature enters the square, disturbs the coins, or mixes them with real coins, the coins detonate. Each creature within 10 ft of the coins must make a DC 14 Dexterity saving throw, taking 3d6 fire damage and 1d6 thunder damage on a failed save, or half as much on a success. The coins are destroyed when they detonate. A creature inspecting the coins can identify them with a DC 15 Intelligence (Investigation) check.