Rise of the Empire: Blaster Squad, Book 5 (Unabridged‪)‬

When Siren and the Kid are reported missing Nick Justice is determined to find them. After learning they are being held on a remote planet known as Poseidon, a water world far from Alliance space, he and his team race to their rescue. 

Blaster Squad soon finds themselves having to fight for survival. Someone is determined to stop them and Nick suspects the mysterious figure known as the Master is behind the attacks. They soon discover the Master is plotting to overthrow the galaxy and rule as Emperor throwing civilization into a new dark age ruled by terror and fear. 

Nick Justice and Blaster Squad are determined to stop them or die trying.