The Gelmorrans lived fine underground for so long because the Elementals could rage up above all they liked, Gelmorra was outside of their jurisdiction (and therefore outside of their power).
Once the Gridanians started living in the surface world, the Gelmorrans could no longer live as they always had without causing severe danger and loss of life to those up above.
An angry Elemental doesn't care that it's the people under the ground causing the disturbance - they also don't care if it's a child, or someone with no choice. They just comprehend that their will is not "being done".
Those who live in the surface Twelveswood will always be subject to Elemental-wrought consequences from the actions of those who visit the Twelveswood or who live at its fringes.
If your take-away from this is that Elementals are dicks, then you're not alone.
Once the Gridanians started living in the surface world, the Gelmorrans could no longer live as they always had without causing severe danger and loss of life to those up above.
An angry Elemental doesn't care that it's the people under the ground causing the disturbance - they also don't care if it's a child, or someone with no choice. They just comprehend that their will is not "being done".
Those who live in the surface Twelveswood will always be subject to Elemental-wrought consequences from the actions of those who visit the Twelveswood or who live at its fringes.
If your take-away from this is that Elementals are dicks, then you're not alone.