Tier 2 Epic transmutation

Casting Time: 1 action
Range: 120 feet
Components: V, S, M (an obsidian figurine in the shape of a dragon)
Duration: Concentration, up to 1 minute

You superheat the ground of an area within range, converting it to molten lava. The area of lava is difficult terrain and consists of ten 10-foot cubes, each of which must have been previously occupied by ground and be adjacent to at least one other cube. When a creature enters the area for the first time on its turn or starts its turn there, it takes 20d8 points of fire damage and must attempt a Constitution saving throw or be incapacitated by the extreme heat until the start of its next turn. A successful saving throw halves the damage and prevents the incapacitated condition.

At the start of each of your turns while you concentrate on this spell, the fire damage dealt by the spell increases by 2d8 (to a maximum of 40d8) and you may convert two additional 10-foot cubes of ground to lava in spaces you can see adjacent to at least one other cube of lava.

If you concentrate on this spell for its full duration, its duration becomes permanent and forms an active volcanic hotspot.

Ref: ELCR p92