What is Bone Chariot

In chapter six, Jung has a vision in which Freud comes over the dawn riding in a chariot made of the bones of the dead. In the vision the driver of this ancient new-fangled war machine which caused the possibility of mobile archers had to be killed. Jung and his brown-skinned companion whom he called "a savage" were able to achieve this on the level of a vision. In the end he said it was the savage who initiated the attack but that it was needed and that Jung was very glad they functioned as such an excellent team.