A terraqueous globe, Myr'nautilôn's stormy seas rise with the tides of neighboring planets. In a great trench in a whirlpool sea live a shadowlike people, the Sol'yn. Their shallow seas counterparts, the Lid'yn live in the sunlit days. A brotherhood of diplomatic dragonriders, the Hydrobrachians, face an interstellar invader, the Droom, oil-blooded lifeforms vulnerable to water. Their war poisoned the seas with oil blood, leaving the resistance to the remaining Sol'yn, Lid'yn, and Hydrobrachians.