Cutrock

No one knows how large the hobgoblin-led city of Cutrock truly is. Located deep in the Giantspire Mountains, Cutrock stretches deep under the earth into the Shallows of the Underdark.
Though the Hobgoblin General has changed several times over the last decade, each is advised by the Demon Queen of Cutrock known as Soneillon. While the Demon Queen holds a deep and abiding hatred for the Realm of Impiltur, the hobgoblins raid into Narfell and Damara often, but never in numbers enough to demand a counterattack.
Any reasonable assault on the Giantspires would have to be a joint effort, uniting forces from Damara, Impiltur, and Narfell. Even if that were managed, it's likely the hobgoblins would remain numerous. If the nations want the wealth of the Giantspires, then miners will have to seek out inconspicuous and defensible positions in spite of the dangers.