The Chimera of Immernacht by C.L. Carner

Queen Sophie begins to suspect her consort, Bastian, may be keeping a dark secret. She still hasn't met his family, and he is always leaving for days at a time to conduct "business" on the mysterious island of Immernacht-a place rumored to be the magical prison of bloodthirsty monsters. Her suspicion grows when a body washes up on the shore near Blackwater drained of blood and she is forced to tell Bastian that her father, Leon Rend, is preparing the Silver Talons for war with Immernacht. Can Bastian prove his innocence to her, despite his family's secret, or will Sophie join the war against him?