From the back cover:
Powers & Principalities is an essential companion to Babylon 5: A Call to Arms, 2nd edition. Packed full of new rules, scenarios, campaigns, and exclusive background material, this supplement will transform your games and give you more tactical flexibility with your fleets.
Inside you will find:
Fleet Command: A Wealth of unique rules for fleets, stressing the indivicuality of each race. Start playing with Abbai mines, Shadow screams, and many more!
New Ships: All new variants of your favourite ships, tweaked for specific tactical duties.
The Gaim Intelligence: The complete Gaim fleet list, allowing you to bring the Hive Mind to the tabletop.
Space Stations: Build your own space station, for any fleet, with an easy to use construction system.
Unique Admirals: Powerful heroes who can influence an entire battle.
New Background Material: Never published before source material, uncovering the secrets of the Earth-Minbari War and the Narn fleet.