There's only one main character in this book: Cassandra. The reason for this is that she is moved from group to group of Setari for training and only really bonds with one group called First Squad. In this Squad, there are 3 main characters who are all pretty different: Zee, Lohn, and Maze.
Zee-female with brown hair and eyes in her mid 20's who is very sassy and humorous, but when she's busy, she is very business-like and the others make fun of her for it.
Lohn- tall man with short, brown hair who is known as a flirt. He is very bossy and demanding; he doesn't like listening to others and what they have to say. Lohn is also in his mid 20's
Maze- Very burly man with a strong build and beard in his late 30's who is the leader of First Squad. He is a very capable Setari with many talents and is very nice and caring towards Cassandra. He lost his wife in action and is very sensitive since this event.
Cassandra- 17 year old female high school student who lives in Sydney, Australia. She is a very quirky and humorous