After evacuating everyone from the underground, Duanmu Huai activated the Ground Fire System, filling the entire underground tunnel with magma. Though this was tantamount to creating an artificial volcano—there aren't many people left on this continent now, are there?
The condition of the rescued prisoners was not very good.
Many of the prisoners had been brain-transformed by the Beast Race. Their frontal lobes were removed, turning them into docile living dead. Duanmu Huai promptly granted these slaves their final humanitarian light. Others hadn't been transformed, but they had endured the Beast Race's brutal torture. Some even chose suicide after being rescued.
Nevertheless, some people came out alive, returning to the surface.