The appearance of the Orks was unexpected and this element gave them the ability to overthrow the Dwarves. While Elves retreated in the face of the Orks, the stubborness of Dwarves proved all too tempting to the ill-tempered Ork. They drove deep into the Old Dominion, bringing an end to the climax of Dwarf civilization.
The ork numbers have since withered, through infighting and the dangers left behind by dwarves abandoning their homes. Their hordes remain content within the mountains, on top of their prize while their need for violence is satisfied by ambushing greedy scavengers searching for lost Dwarven treasure.