Overthrown - Secrets of the Empire, #4

Three rivals in an empire make desperate choices to repel an alien invasion. In the wake of the Siege of Alveolar, the Istevor Diamond has failed. Freed from their prisons, the giant insectile Chosen overrun multiple sectors of the Aura Empire. In order to hold them back, or inflict a decisive blow that will show the strength of humanity, Vespasian Shiraan must protect the woman who might hold all the answers and finally make his play for the throne that he has held off until the right moment.
Duke Caspian Acratani claims to have communion with the Chosen and a beneficial, though temporary, alliance. While he goes steadily mad from the voice in his head, Deirdre Istevor, part of the most powerful House in the Empire, keeps a steady eye on him. If he still has some sanity she will find it. She believes she's playing him, but she may be wrong. Amid this minefield of schemes, Rochelle Sarakshi, lieutenant in Vespasian's special op squad, explores an old mystery from her brother's past which provides answers to the Chosen's rulers, and a weapon hidden away years ago by a traitor.
When a maze of flesh reveals the weapon's hiding place, the Imperials must make a decision that will ripple throughout their lives: do they wield the weapon, or do they destroy it?