Stonefire (spell)

Stonefire  was a divine evocation spell that would ignite natural, non-living stone as directed by it's caster. When cast, the stone would combust, emitting a thick black smoke and radiating destructive heat that was especially damaging to the undead.

Ignited stone would take structural damage for as long as the fires burned. Given enough time stonefire could burn through stone walls, columns or any other rocky structure causing buildings or caves to collapse in on themselves.