Radiant King, The

This is the first book in the Astral Kingdoms trilogy, an epic fantasy tale featuring six immortal siblings who wield the mysterious power of radiance. Five of them have sworn to peace, but one, Eder, seeks a throne and spreads a cruel faith across the land. The story follows Faron, another sibling, as he returns from exile to stop Eder, with the help of their calculating brother Sariel and a fanatical ruler known as the Bastard Princess.