The Eastbound group is formed in season 4 leading the team east with Roberta Warren as guide, due to her visions of the Black Rainbow.
The Eastbound group is a group of zombie apocalypse survivors who have banded together. The group is comprised of individuals from all walks of humanity, many with a history and past feuds.
The mission is unclear even to Warren. All she knows is that she need to prevent an upcomming catastrophe.