Volcanic Core

You open a portal to the hottest part in the Plane of Fire, which releases a torrent of flame and destruction. Anything caught in a 25ft radius and 30ft tall cylinder must succeed on a dexterity saving throw taking 20d8 fire damage on a failed and half as much on a success. Any creature killed by the spell is turned to ash. Anything flammable caught in the area of effect is disintegrated and anything flammable with 10ft of effect catches on fire.