The Underground Geode

The underground geode is the place the comm Castrima selects as its living quarters. Ykka tells Essun that when they discovered the geode it was full of the skeletons of people who had lived there previously. Essun is uncomfortable living in a place where its predecessors all obviously died, but Ykka assures her the people in the comm were also uncomfortable at first. They had come to the decision it was safer for them to live below ground than to try to defend themselves above ground.