Spell: bonfire

Pretty simple idea. It's just a spell that causes a fire, it burns for a long time and does progressive damage the longer it burns. It acts a lot like the poison spell except for the fact that it can damage walls and buildings as well as any cc troops standing in the effected area. It should be able to burn for a long time, around a minute and a half, but never do enough damage on its own to destroy most buildings. Maybe the basic spell should start at around 600 damage over 90 seconds. Multiple spells don't amplify effects, they just do their own damage on top of the others. It also should be a two space spell, whether a dark spell or not, that way you couldn't stack 9 of them on top of each other, as that would most certainly be way too op.