This one is called EXILED. It's a traditional fantasy with a mystery, set in a empire called Tosquia.
Two exiled princes must unite and face their own legacies of cruelty to save an undeserving empire from invasion.
Ijikaelfen Prince Ashetan is a coddled seventh son who beds a different lady every night. The only battle he's ever seen has been in festival tournaments. But when enemy Dokkaelfes invade, massacring the Ijikaelfes, a loyal servant spirits him away from his island home to the Tosquin Empire. Cursed into silence by vicious Dokkaelfen magic, Ashetan believes he is the last of his kind.
Until he meets Ereq.
High Lord Ereq, whose slitted pupils mark him as a carrier of Ijikaelfen blood, is a bastard cousin to his best friend, the Tosquin prince. Ereq's position as third in line to the throne provides him with plenty of enemies, and his odd eyes and irreproachable honor doesn’t help his cause against a sea of jealous courtiers vying for the Emperor’s affections.
While searching for Senyan raiders, Ereq finds Ashetan lost and alone in the wild deserts. A foolhardy battle-lord challenges Ashetan to a dual. Ashetan wins it, and by tradition, earns ownership of his house and wives. Uncertain what to do with this strange, pale creature, Ereq takes Ashetan to the Prince. But the Prince is distracted by a tryst with his betrothed, and before he can decide Ashetan’s fate, he’s brutally murdered.
Mad with grief, the Emperor accuses Ereq of the murder. Ashetan, bound by his own princely vows to protect one of his own, determines to rescue Ereq, who resolves to find the true killer. Together, they must brave vicious courtiers, the wilds of Tosquia, and the storms of a foreign court to find the murderer, as well as install the true heir on the Tosquin throne.