From the back cover:

Caste Book: Night is fourth in the Caste Book line for Exalted - books detailing the different Castes of the Solar Exalted. Within its pages are all the secrets of the Zenith Caste, from their Charms of Stealth and Agility to their fragmentary memories of the First Age. The book contains new Charms, rules and artifacts to help them carry out their holy mission.