Eruption

A pillar of lava erupts in a 10ft radius, 30ft-high cylinder centred on a point within range.
All creatures within the cylinder must make a Dexterity saving throw. A creature takes 10d6 + 20 fire damage on a failed save and have as much damage on a successful one. Any creature wearing heavy armour suffers an additional 2d8 fire damage as the metal components overheat and fuse.
The ground in the radius becomes difficult terrain.
When you cast this spell using a spell slot of 7th level or higher, the damage increases by 1d6 for each slot level above 6th.