From publisher blurb:
Fellowship is a game for 3-6 players about going on an adventure, in the same vein as Lord of the Rings or Wakfu or Jojo's Bizarre Adventure: Stardust Crusaders. The system is loosely based on the Apocalypse Engine. This is the third book in the Fellowship line, an expansion to the first game. You will need the first book to play with the content found in Book 3. You do not need Book 2, but can use its content alongside the content found here in Book 3.
In Rebellion is an expansion book for Fellowship. Within this book, you will find 6 new Fellowship playbooks, a replacement Overlord playbook, and a new kind of playbook, a Team playbook, used by the entire Fellowship cooperatively. There's also a slew of new Destinies, Threats, and Set Pieces, as well as The Nemesis, a new type of playbook that adds another player who works with the Overlord or the Empire against the fellowship.
The Empire is an alternative to the Overlord playbook. Rather than stop an evil overlord from destroying the world as we know it, the Empire has already conquered the world. They succeeded. The fellowship must work as a rebel alliance to overthrow the iron grip of the fascist Empire and destroy them from the inside out. They have sources of power that empower the entire Empire as long as they stay standing, and Leaders who inspire their soldiers and make them stronger. Both their power sources and leaders must be destroyed or defeated to make the Empire collapse.