Fena's choice was to leave the world as it was so that the Goblin Knights would be safe, being unable to bear the thought of saving Yukimaru but letting the others die. This is fine and good in the present, but it means there will continue being new Maidens of Choosing in the future, and eventually one with less optimism than Fena will likely choose to destroy the world. Humanity as it is is living on borrowed time.
