Book is a warforged warlord built to teach rookie Bahamut Patrollers the ropes of small unit combat tactics. He a first generation training aid therefore looks aged when juxtaposed with the other newer training aids.
He is fully sentient and has found a best friend in Siti, a cleric of Bahamut. Together they see the first missions of many rookie Bahamut Patroller’s with a 0% casualty rate.
Book left the party with Siti to help her establish a temple of Bahamut in Winterhaven in episode 2.