In a nation known as Avilonía, the land is ruled by monarchs known as the God-given, who have been blessed by elemental gods long ago, during a time of great war. After a brief moment of peace, Sebastián Eliódor murdered his brother - the last Sun King - in cold blood. He rose to tyranny, took over the land with dark magic, thus pushing the rest of the God-given to leave and split the land in half. Now, only the Moon and Air Kingdoms remain. Over 20 years later, a new war rages on in what is now known as The Rift, in an effort to recover stolen land and to to keep Sebastián Eliódor at bay. In the coastal city of Coáraluna, the capital city of the Moon Kingdom, opera singer, Esmé Vespertín, is a shy refugee who takes a potion for her recurring headaches that cause her to see strange shadows. In her eyes, she is just a normal girl who is trying to get by with her ailment in a world that could crumble at any given moment. Yet, she harbors a big secret that not even her closest friends know the details of: she’s been entertaining a secret relationship with none other than Río Maximiliano Markaél - Avilonía’s Moon Prince. Principe Río has been trying to prove himself by going off on secret missions for his father, Rey Adrián, to help on the war front. However, on his latest mission, he took on an ambitious task and came back half alive with a cursed object that could change the course of the war forever. However, when Esmé finds it by accident, things take a turn, and on the night of the yearly Winter Solstice Ball, an attack on the palace reveals that she may be more special - or terrifying - than anyone could have imagined.