Acid rupture

Make a geyser of acid, coming up from the Ground dealing 4d8 +6 damage and making the 5 ft difficult terrain. Anyone passing through, or starting their turn in, this difficult terrain Will take 1d8 acid damage that cant be blocked, this also reaches 15 feet into the air. On your turn, you may use a bonus action to stop the geyser from spewing out acid, and then noone Will take damage from it and it wont be difficult terrain anymore. Enemies hit by the initial attack Will have to make a dex save of 14 or they take full damage.