The Dravenhart family suppresses younger daughter Aurora's true dragon blood and presents elder daughter Celeste with a forged mark as heir. When two gods propose, they marry Celeste to the light god Aurelius and send discarded Aurora as a substitute bride to the feared underworld king Kaelen. Aurora finds respect in the underworld and awakens under an ancient shadow dragon's guidance, while Celeste discovers Aurelius is an abusive false god sustained by sacrifice. At the annual banquet Aurora fully transforms, and Kaelen exposes both Aurelius and the family's bloodline fraud. Aurora abandons her birth family, is crowned queen of the underworld and dragon heir, and reconciles with her sister after her escape.
