Siege!
You call in the best engineers and carpenters from the land and have them produce for you five massive trebuchets. They are capable of hurling stones as far as the eye can see and further than any catapults that were known to have been left within the fortress. The high to which these rocks shall be hurled shall give them the force of a meteorite when they strike down. Once the five are ready they are moved within siege range of the fortress.
The first couple volleys of rocks are off mark, landing harmlessly in the barren field between both armies. After several volleys adjustments are made and the first boulders begin to slam against the walls of the fortress. They seem not to leave a mark, and each successive rock bounces harmlessly off the side of the fortress. Rock after rock is hurled into the side but to no avail. After hours of hurling rocks fails to damage the walls you have them start hurling rocks into the actual fortress in an attempt to soften up enemy forces. You continue this attack for another hour as the sun starts to set. Then, you notice a bright light launch from the fortress and in a perfect arch land dead on one of the trebuchets. It immediately engulfs the weapon in flames. Three minutes later a second bolt of fire arch's across the sky and decimates a second trebuchet. You quickly order the retreat of the other three but one is destroyed before it is able to finish packing.
Had the forest people constructed a trebuchet of their own and launched a ball filled with burning oil? Or had they used some sort of demonic magic. This you do not know but what you do know is a new strategy beyond mortal siege weapons shall have to be implemented.
The first couple volleys of rocks are off mark, landing harmlessly in the barren field between both armies. After several volleys adjustments are made and the first boulders begin to slam against the walls of the fortress. They seem not to leave a mark, and each successive rock bounces harmlessly off the side of the fortress. Rock after rock is hurled into the side but to no avail. After hours of hurling rocks fails to damage the walls you have them start hurling rocks into the actual fortress in an attempt to soften up enemy forces. You continue this attack for another hour as the sun starts to set. Then, you notice a bright light launch from the fortress and in a perfect arch land dead on one of the trebuchets. It immediately engulfs the weapon in flames. Three minutes later a second bolt of fire arch's across the sky and decimates a second trebuchet. You quickly order the retreat of the other three but one is destroyed before it is able to finish packing.
Had the forest people constructed a trebuchet of their own and launched a ball filled with burning oil? Or had they used some sort of demonic magic. This you do not know but what you do know is a new strategy beyond mortal siege weapons shall have to be implemented.