Married to the Foolish War God

Seraphina Sutton marries mentally impaired Prince Landon Shaw. She takes control, deals with Empress Dowager/Third Prince, discovering Landon's skills. She uses First-Third Prince struggle to expose Third Prince's corruption/Lavinia Sutton's plot. Landon regains senses; they join forces. Landon consolidates power at frontier; Seraphina schemes in capital, luring First Prince/Empress into coup. Landon quells rebellion, ascends throne as Emperor, cures Seraphina's leg; they rule.