The demon mentioned that the ruby jeweled eyes got entangled with a demon causing them to massacre a lot of people. In chapter 20, the ruby jeweled eyes ability was that they can make strong weapons with their blood. The power was wanted by many other countries, so a war was waged cause of it. The ruby jeweled eyes, fought in the war and in the end they used their own blood to kill themselves.
The demon mentioned that the ruby jeweled eyes got entangled with a demon causing them to massacre a lot of people. In chapter 20, the ruby jeweled eyes ability was that they can make strong weapons with their blood. The power was wanted by many other countries, so a war was waged cause of it. The ruby jeweled eyes, fought in the war and in the end they used their own blood to kill themselves.