Coming of the Shadow

After centuries of peace, war is coming to the sister nations of Eldir and Efrim. Not a brief border squabble easily won, but a war with dark creatures the like of which have only been seen in nightmares. Creatures who bring with them a sickness not even the master healers of Eldir know how to cure.
This story centers around seven young adults who have been friends since childhood, three young men and four young women, including the royal children of both nations.
Prince Aranin and Princess Analisia of Efrim are twins, but their culture renders their position in life almost opposite. She is being groomed as crown princess, although her inclinations stray from tradition. He has no rank but is expected to follow in his fathers footsteps as a soldier even though he prefers art.
Princess Tatyana of Eldir is desperate to earn the title she has worked for all her life, while her younger brother Sebastian has reservations about earning his. He must follow his duty, even though his heart goes with Helen.
Helen and Elisabeth are sisters but very different. Elisabeth longs for battle, glory, and heroism, while Helen dreads what is coming.
For his part Joseph, Sebastian's best friend from childhood, doesn't think about the dark. He can't. He prefers joking and being silly, and the world is still perfect. But not for long.
When the dark comes, will they have the strength to endure the coming trials, and to take their places in the defense of their people?