Comet rain

Upon casting, 10 comets each dealing 8d10 fire damage over an area of 100x100ft. Also does 5d10 bludgeoning damage if creatures are directly impacted. Each one explodes, which can affect the material it impacts depending on the type (Dirt, stone, and light metals will be melted/destroyed accordingly to the material. Creatures that are not directly hit are dealt the fire damage only and each comet impact zone has a 30ft diameter. Impact zone is considered difficult terrain after the comet impacts it (it explodes, leaving no remains behind) and is very hot, but not enough to deal damage, if standing nearby, but if entered deals 1d12 fire damage for each turn spent in the zone.