Built during the Great War. The Fortress was made as a both a refuge for people having lost their homes, and as a camp for soldiers to rest before embarking onto the frontlines of war. Deep under the fortress massive housing quarters were constructed, training grounds were built for dwarves to hone their abilities and martial prowess.
The dwarves held this place of defense for years during the war. Until a combined assault of orcs, ettins, and viscous wereboar broke their defenses and forced the dwarves to retreat, fleeing through caves and tunnels under the surface and caved in to prevent being tracked down.