Aganazzar's Lava Flow

A gigantic wave of searing hot liquid surges out from your hand in a 300 ft. cone. Any creature caught in the area when the spell is cast must make a Strength saving throw or take 8d6 bludgeoning damage and be knocked prone by the sheer force of the wave hitting them. After this wave rushes through the target area, it leaves behind an area of difficult terrain and lava. For the next 10 minutes, any creature that enters the area for the first time or starts its turn there must make a Dexterity saving throw, taking 8d6 fire damage, or half as much on a successful saving throw.