Wu's Eruption

The arcane energy of flame condenses within you as you expell molten magma out into an area within range that covers a total of 20ft area. This area can be separated into individual 5ft x 5ft squares, a straight 20ft x 5ft line, a 10ft x 10ft square, etc. 

This magical magma acts as rough terrain and any creature that passes through the magma takes 4d6 fire damage. If a creature ends their turn in the magma or they are occupying the space of the magma when the spell is cast, they must make a dexterity saving throw or take 4d10 fire damage. The target takes half damage on a successful save. 

At higher levels the amount of magical magma increases. The spell creates an additional 5ft x 5ft square per two spell levels.