It was a strengthened version of the earth fire eruption spell!
The spell wasn't the best choice to deal area damage, mainly because it required too much time to cast.
At first, one had to condense magic power beneath the ground and heat it, until the flames and magma erupted from the soil.
It was extremely powerful, but during the long period of magic power concentration, anyone who wasn't an idiot would sense the magic power below as well as the rising temperature of the ground.
Then they would flee.
This spell could be used to deal with immobile targets, such as buildings.
But that was only if the enemy had no Mages, because the concentration of flames required delicate magic control that could easily falter if someone disrupted it.
Therefore… The spell was mainly used to deal with military garrisons that had no Mages, or huge buildings in the enemy's possession.
